Introduction to JavaScript: Programming Basics, Expressions, Functions (40/40

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Introduction to JavaScript
Apostolos Syropoulos
Xanthi, Greece
asyropoulos@yahoo.com
Introduction to JavaScript for members of the
Erasmus+ founded project GAMES

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Presentation Outline
1 Programming Languages
2 Basics of JavaScript
3 Expressions and Operators
4 Basic Commands
5 Deﬁning New Functions
6 Finale

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Programming Language?

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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A formalism or formal notion used to instruct a computer to
perform a computational task.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Roughly, a computational task is an abstract, mathematical in a
sense, task.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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sense, task.
Philosophical question: Is falling in love a computational task?

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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sense, task.
Surprisingly, computationalism—the view that mental states are
computational states—has many followers.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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sense, task.
On the other hand, Jaak Panksepp asks: Could you compute me
an orgasm?

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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sense, task.
an orgasm?
Back to business: Computers can calculate and enumerate and
that’s what we do with programming languages.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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sense, task.
an orgasm?
Back to business: Computers can calculate and enumerate and
that’s what we do with programming languages.
Niklaus Wirth did not like the term programming language.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Characteristics of Programming Languages

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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How computational tasks are described?

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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By a sequence of commands? The language is imperative.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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By objects and their interactions? The language is
object-oriented.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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object-oriented.
By functions and their composition? The language is functional.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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object-oriented.
By a set of sentences in logical form? Then it is a logic
programming language

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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object-oriented.
Specifying a programming language means to: describe its
syntax and its semantics.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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object-oriented.
Syntax: the way we arrange “linguistic” elements in a program.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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object-oriented.
Syntax: the way we arrange “linguistic” elements in a program.
Semantics: the computational eﬀect of each structure.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Some popular programming languages

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Old languages:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Old languages: FORTRAN,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Old languages: FORTRAN, COBOL,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Old languages: FORTRAN, COBOL, PL/1,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Old languages: FORTRAN, COBOL, PL/1, Algol68,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Old languages: FORTRAN, COBOL, PL/1, Algol68, BASIC,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Old languages: FORTRAN, COBOL, PL/1, Algol68, BASIC, LISP,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Timeless languages:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Timeless languages: C,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Timeless languages: C, C++,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Timeless languages: C, C++, Ada,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Timeless languages: C, C++, Ada, Prolog,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Timeless languages: C, C++, Ada, Prolog, SML.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages: Java,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages: Java, JavaScript,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages: Java, JavaScript, Perl,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages: Java, JavaScript, Perl, Python,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages: Java, JavaScript, Perl, Python, Ruby,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages: Java, JavaScript, Perl, Python, Ruby, C#,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Pascal.
Modern languages: Java, JavaScript, Perl, Python, Ruby, C#,
Haskell.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is Programming?

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Programming is the mental activity by which we express the
solution to a given (mathematical) problem in some
programming language.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Defining New
Functions
Finale
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The difficult part is to solve the problem with specific tools.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Programming is not something you learn by following a recipe or
a method.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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a method.
Programming is both a craft and a science.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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a method.
It is a craft (or art!) because there are no rules of thumb that one
can follow to solve a problem.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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a method.
A programmer is a scientist if mathematicians are scientists.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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a method.
Intuition plays a very important when solving a problem.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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a method.
Intuition plays a very important when solving a problem.
The implementation of a solution requires the knowledge of
common techniques and practicers.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Steps Involved in Programming

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Deﬁning the problem.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Outlining and structuring the solution.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Selecting solution methods.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Coding.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Coding.
Debugging.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Coding.
Debugging.
Testing and verifying.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Coding.
Debugging.
Documenting.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Coding.
Debugging.
Documenting.
Maintaining the program.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is JavaScript?

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is JavaScript?
It is an object-oriented programming language initially designed
and implemented by Netscape.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is JavaScript?
The language is the most widely used language for client-side
scripting of web pages.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is JavaScript?
HTML5 and all relatively older versions of HTML support tge
<script>

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is JavaScript?
<script>
JavaScript can be used to make dynamic web pages.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is JavaScript?
<script>
JavaScript can be used to make dynamic web pages.
JavaScript and Java are object-oriented languages but that is
their only similarity.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Adding JavaScript Code to HTML Content

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Here is how we can embed JavaScript code:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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<script>
JavaScript commands…
</script>
<noscript> WARNING</noscript>

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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<script>
</script>
Alternatively

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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<script>
</script>
Alternatively
…
<head>
<title>My Page</title>
<script src="common.js">
</script>
</head>
<body>
…

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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A Complete Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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A Complete Example
Here i a complete example:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
.
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A Complete Example
<!DOCTYPE html>
<html> <head>
<meta charset="UTF-8">
<title>Example</title>
</head><body>
<script>
document.write("Hello, net!")
</script>
<noscript>No JavaScript support.</noscript>
<p>That's all, folks.</p>
</body> </html>

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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A Complete Example
<!DOCTYPE html>
<html> <head>
<meta charset="UTF-8">
<title>Example</title>
</head><body>
<script>
document.write("Hello, net!")
</script>
<noscript>No JavaScript support.</noscript>
<p>That's all, folks.</p>
</body> </html>
Open your text-editor, type the code, save the ﬁle and open it with
your browser.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Values

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Values
Numbers, that is, quantities like 41 or 3.14159.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Values
Boolean (logical) values, that is, the values true and false.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Values
Sequences of character like "Hello!" that are known as strings.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Values
A string must be enclosed in either single or double quotation
marks, for instance, "John's girlfriend." or
'Mary came!'.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Values
'Mary came!'.
The value null, which denotes a no value.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Values
'Mary came!'.
The value null, which denotes a no value.
The value undefined, which denotes an undeﬁned value.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Variables

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Variables
A variable is a name that is used to designate a value.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Variables
In mathematics we write 𝜋 to designate the number
3.1415926535897 ….

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Variables
3.1415926535897 ….
A variable is actually the name of some storage location where a
value is stored.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Variables
3.1415926535897 ….
value is stored.
Variables do not designate the same value but time passes may
designate a diﬀerent value.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Defining New
Functions
Finale
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Variables
3.1415926535897 ….
value is stored.
Think of a process that counts objects. In different times, it will
hold different values.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Variables
3.1415926535897 ….
value is stored.
The ﬁrst character of the name of a variable must be a letter

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Variables
3.1415926535897 ….
value is stored.
The ﬁrst character of the name of a variable must be a letter
If there are more characters in a name they should be letters,
digits, or the symbol _ (underscore).

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables
A variable can be introduced with an assignment or a declaration.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables
Assignment: variable = value.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables
Declaration: var variable.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables
Thus the command x = 3 assigns the value 3 to variable x.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables
The command x = x + 1 assigns the current value of x plus 1
to variable x.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables
to variable x.
The command var y declares variable y and its value becomes
undefined.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Using Variables
to variable x.
The command var y declares variable y and its value becomes
undefined.
Find the ﬁnal values of the various variables after these
commands have been executed.
x=4
y=6
z=2*x // * denotes multiplication
x=x+1

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
valueA @ valueB, where @ is a comparison operator.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
The standard comparison operators are:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
<= (less than or equal to), and

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
>= (greater than or equal to).

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
Suppose that x = 5 and var y were just executed. Then,

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
x == 5 evaluates to true;

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
x != 5 evaluates to false;

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
x < 5 evaluates to true;

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
y == underfined evaluates to true;

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Comparisons
== (equal to),
!= (not equal to),
< (less than),
> (greater than),
y == underfined evaluates to true;
x <= 5 evaluates to true.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Arrays

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Arrays
An array is a special variable that can hold more than one value at
a time.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Arrays
a time.
Each value is assigned to an element of an array and one can refer
to an array by its index.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Arrays
a time.
To create an array, write the name of the array, the symbol =, and
the values that will be stored to the array in square brackets
separated by comma:
coffees = ["French Roast", "Columbian",
"Kona"]

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Arrays
a time.
To create an array, write the name of the array, the symbol =, and
the values that will be stored to the array in square brackets
separated by comma:
coffees = ["French Roast", "Columbian",
"Kona"]
To print the second element of this array, use the following
command:
document.writeln(coffees[0])

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Strings

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Strings
A sequences of character like "Hello!".

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Strings
A string must be enclosed in quotation marks: either single or
double quotation marks.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
.
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Strings
Strings consist of simple ASCII characters, escape sequences, or
Unicode characters.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Strings
Unicode characters.
An escape sequence corresponds to a special character that
cannot be entered conventionally (e.g., the ESC key).

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Strings
Unicode characters.
An escape sequence corresponds to a special character that
cannot be entered conventionally (e.g., the ESC key).
Escape sequences consist of a backslash followed by a single
letter (e.g., b).

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Assignment Operators

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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An assignment operator stores the value that is on the right of the
operator to the storage location designated by the variable on
the left of the operator.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The basic assignment operators are:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The expression x += y is shorthand for x = x + y.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Similarly, x -= y is shorthand for x = x - y;

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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x *= y is shorthand for x = x * y;

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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x /= y is shorthand for x = x / y; and

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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x /= y is shorthand for x = x / y; and
x %= y is shorthand for x = x % y.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Arithmetic Operators

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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x % y

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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x % y Yields the reminder of the integer division of x by y.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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x++

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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x++ Yields the value of x and then increases the value of x by
one.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
x--

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
x-- Yields the value of x and then decreases the value of x by
one.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
one.
++x

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
one.
++x Increases the value of x by one and yields this new value.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
one.
--x

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
one.
--x Decreases the value of x by one and yields this new value.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
one.
-x

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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one.
one.
-x Yields the opposite of x.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Boolean Operators

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Boolean Operators
x && y

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Boolean Operators
x && y = true only if both x and y evaluate to true.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Boolean Operators
x || y

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Boolean Operators
x || y = true if either x or y evaluate to true.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Boolean Operators
! x

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Boolean Operators
! x = true if x evaluates to false, true otherwise.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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About Commands in General

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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A command is an instruction given by a user telling a computer to
do something.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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do something.
Commands are put together by a programmer to achieve a
speciﬁc task.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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do something.
speciﬁc task.
The basic commands of the language are:

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
.
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do something.
speciﬁc task.
Conditional commands: if...else and swicth.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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do something.
speciﬁc task.
Repetition commands: for, while, do...while, a labeled
command (used in repetition commands without being such a
command), the break command and the continue command.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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do something.
speciﬁc task.
Repetition commands: for, while, do...while, a labeled
command (used in repetition commands without being such a
command), the break command and the continue command.
Comments.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
.
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The if command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
.
.
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The if command
if (condition){
commands
}
if (condition){
commands A
}
else{
commands B
}
Form (a) Form (b)

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
.
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The if command
if (condition){
commands
}
if (condition){
commands A
}
else{
commands B
}
Form (a) Form (b)
Example
if(3>2){
document.write("okey!")
else{
document.write("problem!")
}

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The switch Command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The switch Command
switch (expression){
case label1:
command1;
break;
case label2:
command2;
break;
…
default: commandN;
}

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The for Command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The for Command
for (initialization; condition; inc.-dec.){
commands
}

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The for Command
commands
}
Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The for Command
commands
}
Example
var sum = 0;
for(i=1; i<=100; i++){
sum += i;
}
document.write("<p> 1+2+...+100 = ")
document.write(sum); document.write("</p>")

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The do-while Command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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do {
commands
} while (condition)

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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do {
commands
} while (condition)
Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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do {
commands
} while (condition)
Example
i=0;
do{
i++;
document.writeln(i);
}while (i<=5);

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The while Command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The while Command
while (condition){
commands
}

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The while Command
while (condition){
commands
}
Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The while Command
while (condition){
commands
}
Example
i=1;
while (i<=5){
document.writeln(i);
i++;
};

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Labels

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Labels
label: command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Labels
label: command
Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Labels
label: command
Example
var str = "";
loop1: for (var i = 0; i < 5; i++) {
if (i === 1) {
continue loop1;
}
str = str + i;
}
documemt.write(str);

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The break command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The break command
break or break label

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The break command
Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The break command
Example
for (i=0; i < a.length; i++) {
if (a[i] == theValue) {
break;
}
}

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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The continue command

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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continue or continue label

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Example
i = 0
n = 0
while (i < 5) {
i++
if (i == 3) {
continue
}
document.write(n); document.write(" ")
n += i
}

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Function?

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Function?
A set is a collection of things (e.g., numbers, objects, people, etc.).

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Function?
A function is a relation between the elements of two or more sets.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Function?
A function from a set 𝐴 to a set 𝐵 maps every element of 𝐴 to one
and only one element of 𝐵.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Function?
To deﬁne a function mathematically, we have to write something
like minus(𝑥) = −𝑥.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Function?
The letter 𝑥 is called a parameter, while the 5 in minus(5) is called
argument.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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What is a Function?
The letter 𝑥 is called a parameter, while the 5 in minus(5) is called
argument.
In computer jargon we say a function returns a value and we
mean the value that the function maps its argument.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Defining New
Functions
Finale
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New Functions
To define a function we first type the word function.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions
Then, the name of the function, which should be no diﬀerent
than a variable name.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions
Α sequence of parameters separated by comma surrounded by
parantheses.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions
parantheses.
Τhe body of the function that is used to map the arguments to a
value or values. Typically, the body contains many commands
and is surrounded by curly brackets.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions
parantheses.
Τhe body of the function that is used to map the arguments to a
value or values. Typically, the body contains many commands
and is surrounded by curly brackets.
Example:
function square(number){
return number*number
}

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions cont.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions cont.
Command return interrupts the execution and forces the
function to map the argument to what follows this word.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions cont.
We can use the function we deﬁned in the previous slide as
follows:
x = square(3)

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions cont.
follows:
x = square(3)
Obviously, this command assigns the number 9 to variable x

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions cont.
follows:
x = square(3)
Functions in JavaScript can be recursive, that is, they can be
deﬁned in terms of themselves.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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New Functions cont.
follows:
x = square(3)
Functions in JavaScript can be recursive, that is, they can be
deﬁned in terms of themselves.
However, I will not discuss them here.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling
An event is an action or occurrence that happens in the system
one is programming.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling
one is programming.
A system informs programs about events and so one can
program then to respond to them in some way if desired.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling
one is programming.
If a user clicks a button on a web page, a program might respond
to that action by displaying an information box.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling
one is programming.
In order to deﬁne an event handler we need something that will
trigger an event.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling
one is programming.
trigger an event.
When a user moves the mouse over an area, an event happens.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling
one is programming.
trigger an event.
When a user moves the mouse over an area, an event happens.
To deﬁne an event handler: the name inside a tag followed by an
equal sign, followed by JavaScript code that will be invoked when
the event associated with the handler happens.

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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Event Handling Example

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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<input type="button" value="Calculate"
onClick="compute(this.form)">

Introduction to
JavaScript
Syropoulos
Programming
Languages
Basics of
JavaScript
Expressions and
Operators
Basic Commands
Deﬁning New
Functions
Finale
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<input type="button" value="Calculate"
onClick="compute(this.form)">
When button is clicked, then function compute is called.

Introduction to JavaScript: Programming Basics, Expressions, Functions (40/40

Introduction to JavaScript: Programming Basics, Expressions, Functions (40/40

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Introduction to JavaScript: Programming Basics, Expressions, Functions (40/40