Modern Application Foundations: Underscore and Twitter Bootstrap

Modern Application
Foundations: Underscore
and Twitter Bootstrap
Howard M. Lewis Ship
TWD Consulting
hlship@gmail.com
@hlship
© 2012 Howard M. Lewis Ship

Rich Client
Challenges Make It Work

Make It Work in IE

Make It Right

Make It Pretty

Underscore
Make it work, right
Bootstrap
Make it pretty
Bootstrap.js + jQuery
Make it interact right
Make it work right under IE

❝Underscore is a utility-belt
library for JavaScript …
without extending any of the
built-in JavaScript objects.
It's the tie to go along with
jQuery's tux, and
Backbone.js's
suspenders.❞

Is JavaScript a Functional Language?

© 2008 Hans Splinter – http://www.flickr.com/photos/67196253@N00/2941655917/

underscore.js 1.3.1

Great documentation
34 Kb / < 4 Kb
60+ built-in functions
Uses native support where available
Extensible

Caution: CoffeeScript
CoffeeScript
➠ ❝… a little language that compiles into JavaScript❞
Concise and readable
Optional parenthesis
Implicit returns
Concise function deﬁnitions
Great ﬁt with Underscore!

CoffeeScript: Invoking Functions
$(".x-cancel").tooltip "hide" $(".x-cancel").tooltip("hide")

collection.add new Quiz(originalModel),
at: 0

collection.add(new Quiz(originalModel), {
at: 0
});

CoffeeScript: Deﬁning Functions
function (x, y) {
(x,y) -> x * y return x * y;
}

function isBlank(str) {
isBlank = (str) ->
return _.isNull(str) ||
_.isNull(str) or
_.isUndefined(str) ||
_.isUndefined(str) or
str.trim() === "";
str.trim() is ""
}

_.map list, (x) -> 2 * x _.map(list, function(x) {
return 2 * x;
});

Simple Object / Value
Utilities

Useful Predicates
Predicate Description

isEmpty Is the value null, undefined, the empty string, an empty object, or an empty array?

isElement Is the value a DOM element?

isArray Is the value an array (but not arguments)?

isArguments Is the value the special arguments object?

isFunction Is the value a function?

isString Is the value a string?

isNumber Is the value a number

isBoolean Is the value a boolean?

isDate Is the value a JavaScript Date?

isRegExp Is the value a Regular Expression

isNaN Is the value NaN (note: returns false for undefined)

isNull Is the value null (but not undefined)

isUndefined Is the value specifically undefined

_.isEmpty
_.isEmpty null ➠ true
_.isEmpty undefined ➠ true
_.isEmpty [] ➠ true
_.isEmpty "" ➠ true
_.isEmpty {} ➠ true
_.isEmpty [1] ➠ false

_.isEmpty name:null ➠ false

me = name:"Howard"
delete me.name
_.isEmpty me ➠ true

_.keys, _.values, _.has
me =
firstName: "Howard"
lastName: "Lewis Ship"

_.keys me ➠ ["firstName", "lastName"]

_.values me ➠ ["Howard", "Lewis Ship"]
Just keys for this object, not inherited
Not sorted

_.has me, "firstName" ➠ true
_.has me, "middleName" ➠ false

_.functions

_.functions me ➠ []

_.functions _ ➠ ["after", "all", "any",
"bind", "bindAll", "chain", …
Sorted

_.extend and _.defaults
shape = type: "circle"
➠ {"type": "circle"} extend: last value wins

_.extend shape, { radius: 20 }, { type: "spiral" }
➠ {"radius": 20, "type": "spiral"}

Modifies and returns first parameter

shape = type: "circle"
defaults: first non-null value wins
➠ {"type": "circle"}

_.defaults shape, { radius: 20 }, { type: "spiral" }
➠ {"radius": 20, "type": "circle"}

_.each(list, iterator, [context])
this set to context before invoking iterator

_.each ["alpha", "bravo", "charlie"],
(value, index) ->
console.log "#{value} is at #{index}"
alpha is at 0
bravo is at 1 More CoffeeScript goodness
charlie is at 2
➠ undefined

Alias: _.forEach

iterator function
Callback function passed to Underscore functions
Iterating arrays
value
index
array being iterated
Iterating objects
value
key
object being iterated

context and this
this is a side-effect of method invocation:

anObject.aMethod() ➠ var fn = anObject["aMethod"];
fn.call(anObject)

Sets this for new stack frame

DOM and JQuery manipulate this
➠ Usually the DOM element that triggered event
this not relevant to HOFs
Functions, parameters, local scope
Optional context parameter on many _ functions

_.each(object, iterator, [context])

_.each me, (value, key) ->
console.log "Value for #{key} is #{value}"
Value for firstName is Howard
Value for lastName is Lewis Ship
➠ undefined

_.each(list) and undeﬁned

sparse = []
sparse[10] = "ten"
sparse[20] = "twenty"

_.each sparse, (value, index) ->
console.log "#{value} is at #{index}"
"ten is at 10"
"twenty is at 20"
➠ undefined

_.map(list, iterator, [context])
_.map [1, 2, 3], (value) -> 2 * value
➠[2, 4, 6]

_.map [1, 2, 3, 40, 500],
(value, index) -> value * index
➠[0, 2, 6, 120, 2000]

_.map me,(value, key) ->
"Value for #{key} is #{value}"
➠ ["Value for firstName is Howard",
"Value for lastName is Lewis Ship"]

Alias: _.collect

_.reduce(list, iterator, memo, [context])
aka "accumulator"

_.reduce ["Howard", "Lewis Ship", "TWD Consulting"],
(memo, name) -> memo + name.length
0
➠ 30

"HowardLewis ShipTWD Consulting".length
➠ 30
A side effect!
_.reduce me,
(memo, value, key) -> memo[value] = key ; return memo
{}
➠ {"Howard": "firstName", "Lewis Ship": "lastName"}

Aliases: _.inject, _.foldl

_.ﬁnd(list, iterator, [context])
_.find [1, 2, 3, 4, 5, 6],
(x) -> x % 2 is 0
➠ 2

hand = [
{ value:3, suit: "hearts" }
{ value:2, suit: "spades" }
{ value:7, suit: "spades" }
{ value:8, suit: "diamonds" }
]
➠ …

_.find hand, (card) -> 8 + card.value is 15
➠ {"suit": "spades", "value": 7}

_.find hand, (card) -> 27 + card.value is 31
➠ undefined

Alias: _.detect
© 2009 scribbletaylor – http://www.flickr.com/photos/64958688@N00/3604756480/

_.all(list, iterator, [context])

_.all hand, (card) -> card.value >= 2
➠ true

_.all hand, (card) -> card.suit is "hearts"
➠ false

Alias: _.every

_.any(list, [iterator], [context])

_.any hand, (card) -> card.suit is "clubs"
➠ false

_.any hand, (card) -> card.suit is "diamonds"
➠ true

_.any [] Default iterator is _.identity
➠ false

_.any [false]
➠ false

_.any [true]
➠ true
Alias: _.every

_.ﬁlter(list, iterator, [context])

_.filter hand, (card) -> card.suit is "spades"
➠ [{"suit": "spades", "value": 2},
{"suit": "spades", "value": 7}]

_.reject hand, (card) -> card.suit is "spades"
➠ [{"suit": "hearts", "value": 3},
{"suit": "diamonds", "value": 8}]

Alias: _.select

_.groupBy(list, iterator)

_.groupBy hand, (card) -> card.suit
➠ {"diamonds": [{"suit": "diamonds", "value": 8}],
"hearts": [{"suit": "hearts", "value": 3}],
"spades": [{"suit": "spades", "value": 2},
{"suit": "spades", "value": 7}]}

_.groupBy hand, (card) -> card.value
➠ {"2": [{"suit": "spades", "value": 2}],
"3": [{"suit": "hearts", "value": 3}],
"7": [{"suit": "spades", "value": 7}],
"8": [{"suit": "diamonds", "value": 8}]}

_.groupBy hand, "suit"
➠ {"diamonds": [{"suit": "diamonds", "value": 8}],
"hearts": [{"suit": "hearts", "value": 3}],
"spades": [{"suit": "spades", "value": 2},
{"suit": "spades", "value": 7}]}

_.sortBy(list, iterator, [context])

_.sortBy hand, (card) ->
suitIndex = _.indexOf ["clubs", "diamonds", "hearts", "spades"],
card.suit
100 * suitIndex + card.value
➠ [{"suit": "diamonds", "value": 8},
{"suit": "hearts", "value": 3},
{"suit": "spades", "value": 2},

_.sortBy hand, "propertyName"
Object propertyName has no method 'call'

_.sortBy ["fred", "wilma", "barney"], _.identity
➠ ["barney", "fred", "wilma"]
(x) -> x

_.max(list, [iterator], [context])

_.max [-1, 2, 3]
➠ 3

_.max []
➠ -Infinity

_.max hand, (card) -> card.value
➠ {"suit": "diamonds", "value": 8}

_.min(list, [iterator], [context])
_.min [-1, 2, 3]
➠ -1

_.min []
➠ Infinity

_.min hand, (card) -> card.value
➠ {"suit": "spades", "value": 2}

_.min ["fred", "wilma", "barney"]
➠ NaN

_.include(list, value)

_.include [1, 2, 3], 2
➠ true

_.include [1, 2, 3], 99
➠ false

_.include [1, 2, 3], "2"
➠ false
Uses === comparison

Alias: _.contains

_.pluck(list, propertyName)

_.pluck hand, "value"
➠ [3, 2, 7, 8]

_.pluck hand, "suit"
➠ ["hearts", "spades", "spades", "diamonds"]

_.pluck hand, "score"
➠ [undefined, undefined, undefined, undefined]

_.shufﬂe(list)

_.shuffle hand
➠ [{"suit": "spades", "value": 2},
{"suit": "diamonds", "value": 8},

_.shuffle null
➠ []

Object Oriented Style and
Chaining

_ is a function
Every function on _ is also on
Returns a wrapper object wrapper object

_(hand).pluck "value"
➠ [3, 2, 7, 8]
Wrapped object passed as ﬁrst parameter

_(hand).size()
➠ 4

Chaining Can Be Ugly

_.map(_.first(_.sortBy(hand,cardSortValue).reverse(), 2),
(card) -> "#{card.value} of #{card.suit}")
➠ ["8 of diamonds", "7 of spades"]

1.Sort the hand using the cardSortValue function
2.Reverse the result
3.Take the ﬁrst two cards
4.Convert each card to a string

_.chain(object) and _.value(object)

_.chain(hand)
.sortBy(cardSortValue)
.reverse()
.first(2) Each step returns a new wrapped object
.map((card) -> "#{card.value} of #{card.suit}")
.value()

Flow of Transformations

© 2008 Manu Gómez – http://www.flickr.com/photos/manugomi/2884678938/

_.tap(object, interceptor)

_.chain(hand)
.sortBy(cardSortValue)
.tap(console.log)
.reverse()
.first(2)
.map((card) -> "#{card.value} of #{card.suit}")
.value()
[{"suit": "diamonds", "value": 8},
{"suit": "spades", "value": 7},

Array prototype methods

Extra methods on wrapper not on _

_.([1, 2]).concat "three"
➠ [1, 2, "three"]
concat shift
join slice
pop sort
push splice
reverse unshift

Name Description Aliases

first(array) Return first element in array, as single value head

first(array, n) Return first elements of array as list head

initial(array, [n]) Return everything but last n (default = 1) elements of array

last(array) Return last element in array, as single value

last(array, n) Return last n (default = 1) elements of array

rest(array, [n]) Return array from index n (default = 1) on tail

indexOf(array, value, [isSorted]) Index of value inside array, or -1

lastIndexOf(array, value) Last index of value inside array, or -1

Returns copy with all falsey (null, false, 0, undefined, NaN)
compact(array)
removed

flatten(array, [shallow]) Collapses nested arrays down to a single array

Set Operations

_.without [5, 4, 3, 2, 1], 4, 2
➠ [5, 3, 1]

_.difference [5, 4, 4, 3, 3, 2, 2, 1],
[1, 2],
[4, 10, 22]
➠ [5, 3, 3]

_.union [3, 2, 1, 3, 4, 5], [101, 1], [3, 4], [500]
➠ [3, 2, 1, 4, 5, 101, 500]

_.intersection [5, 4, 4, 3, 3, 2, 2, 1],
[1, 2, 3, 4, 5],
[4, 10, 22, 3]
➠ [4, 3]

_.uniq(array, [isSorted], [iterator])

_.uniq [1, 30, 50, 40, 30, 1]
➠ [1, 30, 50, 40]

_.uniq [1, 30, 50, 40, 30, 1], false, (x) -> "#{x}".length
➠ [1, 30]

_.range([start], stop, [step])
_.range 5
➠ [0, 1, 2, 3, 4]

_.range 3, 5
➠ [3, 4]

_.range 1, 20, 3
➠ [1, 4, 7, 10, 13, 16, 19]

_.range 1, 20, -3
➠ []

_.range 20, 1, -4
➠ [20, 16, 12, 8, 4]

_.zip(*arrays)

_.zip(["a", "b", "c"],
[1, 2, 3],
["alpha", "bravo", "charlie", "delta"])
➠ [["a", 1, "alpha"],
["b", 2, "bravo"],
["c", 3, "charlie"],
[undefined, undefined, "delta"]]

_.bind(fn, context, [*args])

greet = (greeting) -> "#{greeting}: #{this.name}"

greet("Hello, unbound this")
➠ "Hello, unbound this: "

bgreet = _.bind greet, { name: "Howard" }

bgreet "Hello"
➠ "Hello: Howard"

fgreet = _.bind greet, { name: "Mr. Lewis Ship" }, "Salutations"

fgreet()
➠ "Salutations: Mr. Lewis Ship"

_.defer(function)
do invokes the function with no parameters

do ->
_.defer -> console.log "deferred"
console.log "immediate"
immediate
➠ undefined
deferred

_.delay(fn, wait, [*arguments])

log = _.bind console.log, console
do ->
_.delay log, 1000, "delayed"
log "immediate"
immediate
➠ undefined
delayed

About 1 second later

_.wrap(function, interceptor)
timerInterceptor = (wrapped, args...) ->
start = Date.now()
result = wrapped(args...)
elapsed = Date.now() - start
console.log "Function call took #{elapsed} ms."
return result

fib = (x) ->
switch x
when 0 then 0
when 1 then 1
else fib(x - 1) + fib(x - 2)

tfib = _.wrap fib, timerInterceptor

tfib 30
Function call took 23 ms.
➠ 832040

tfib 40
Function call took 2674 ms.
➠ 102334155

More Functions on Functions
bindAll
memoize
throttle
debounce
once
after
compose

Underscore Utilities
Name Description

identity(value) Returns its argument, a default iterator

times(n, iterator) Invoke its iterator n times, passing the index to it

uniqueId([preﬁx]) Creates a unique id, good for labelling DOM elements

escape(string) Converts & < > " ' / in string to HTML entities (& < … )

template(string, [context]) Converts the string into a template function, using a <% … %> syntax

mixin(object) Adds new functions to _ and to the OOP wrapper, for use with _.chain()

Twitter Bootstrap

Built by and for nerds
All skill levels
Desktop, tablets … even smartphones and IE
Custom jQuery Plugins
Based on LESS for customizability

Minimal Setup
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="/bootstrap/css/bootstrap.css">
<script src="/bootstrap/js/bootstrap.js"></script>
</head>
<body>
…
</body>
</html>

12 Column Grid

1 1 1 1 1 1 1 1 1 1 1 1

4 4 4

4 8

6 6

12

940px

12 Column Grid
<div class="container">
<div class="row">
<div class="span2">Span 2</div>
</div>
<div class="row">
<div class="span6 offset1">Span 6 / Offset 1</div>
</div>
</div>

12 Column Grid – Jade
.container
.row
.span2 Span 2
.span8 Span 8
.span2 Span 2
.row
.span6.offset1 Span 6 / Offset 1
.span5 Span 5

Nested Rows
.container
.row
.span2 Span 2
.span8 Span 8 - Level 1 Add up to
.row container
.span4 Span 4 - Level 2 span

.span4 Span 4 - Level 2
.span2 Span 2

Fluid Layout
.container-fluid
.row-fluid
.span2 Span 2
.row-fluid Add up to
12
.span2 Span 2

General Bootstrap Approach

Basic, semantic, markup
Reasonable default look
Simple CSS classes: "row", "span3", "offset1"
Additiive: more CSS classes to tune

Tables
.container
table.span12
caption Bare Table
thead:tr
th.span8 Column A
th Column B
th.span2 Column C
tbody
each row in [1, 2, 3, 4]
tr
each cell in ["A", "B", "C"]
td Cell #{row}-#{cell}

.table.table-bordered.table-condensed.table-striped

Buttons

•Use with:
• <a>
• <button>
• <input type="submit">
• <input type="button">
• <input type="reset">

Glyphicons

<i class="icon-search"/>

.container

Tab ul.nav.nav-tabs
li.active: a(href="#moe", data-toggle="tab") Moe
li: a(href="#larry", data-toggle="tab") Larry
li: a(href="#curly", data-toggle="tab") Curly
.tab-content
.tab-pane.active#moe
h1 Moe Howard
img(src="images/moe.jpg")
.tab-pane#larry
h1 Larry Fine
img(src="images/larry.jpg")
.tab-pane#curly
h1 Curly Howard
img(src="images/curly.jpg")
Text

Requires jQuery and Twitter Bootstrap.js

Dynamic Tabs
ex7.jade
.container
ul.nav.nav-tabs
.tab-content
!= js("ex7")

ex7.coffee
jQuery ($) ->
tabs = $("ul.nav.nav-tabs")
tabContent = $(".tab-content")

_.each ["Moe Howard", "Larry Fine", "Curly Howard"],
(name) ->
…

tabs.find("li:first").addClass "active"
tabContent.find(".tab-pane:first").addClass "active in"

Dynamic Tabs
_.each ["Moe Howard", "Larry Fine", "Curly Howard"],
(name) ->
firstName = name.split(' ')[0]
uid = _.uniqueId "tab"

tab = $("""
<li>
<a href="##{uid}" data-toggle="tab">
#{firstName}
</a>
</li>
""")
content = $("""
<div class="tab-pane fade" id="#{uid}">
<h1>#{name}</h1>
<img src="images/#{firstName.toLowerCase()}.jpg">
</div>
""")

content.appendTo tabContent
tab.appendTo tabs

Modal Dialogs
ex8.jade
.container
button#danger.btn.btn-danger(data-toggle="modal"
data-target=".x-danger-alert") Do Not Press
.modal.x-danger-alert.fade
.modal-header
a.close(data-dismiss="modal") ×
h3 Why did you press it?
.modal-body
p You pressed the button marked
strong Do Not Press
.
.modal-footer
button.btn.btn-warning(data-dismiss="modal") Continue
button.btn(data-dismiss="modal") Cancel

Alerts
ex8.coffee
jQuery ($) ->
$(".x-danger-alert .btn-warning").on "click", ->
alert = $("""
<div class="alert fade in">
<a class="close" data-dismiss="alert">×</a>
<strong>Well, you pressed it!</strong>
</div>
""")
alert.prependTo $(".container")

Other Plugins

Popover Tooltip

And more:
Scrollspy
Dropdown Button
Collapse
Carousel
Typeahead

Underscore

Effective, functional JavaScript

Bootstrap

Sharp L&F out of the box

Very customizable

Bootstrap JS

Lots of UI pizzaz, effortlessly

CoffeeScript

Concise, readable JavaScript

Modern Application Foundations: Underscore and Twitter Bootstrap

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