2. About duck typing in dynamic
languages:
“My god how you can write a real program
when you just assigning random crap to
another crap and expecting it to work”
– John
Carmack, founder of id Software, developer of
popular game titles like Wolfenstein , Doom, Quake
and Rage, well-known open source
advocate, millionaire.

3. JavaScript is really
complicated language…

4. var a = 012
console.log( a )
→ 10
OMG!

5. console.log( "3" + 1 )
→ "31"
console.log( "3" – 1 )
→2
OMG!!
console.log( "222" - -"111" )
→ "333"
OMG!!!

6. console.log( 9999999999999999 )
→ 10000000000000000
OMG!!!!
console.log( 111111111111111111111 )
→ 111111111111111110000

7. console.log( Math.max() )
→ -Infinity
console.log( Math.min() )
→ Infinity
console.log( new Array([], null, undefined, null) == ",,,"; )
→ true
var foo = [0];
console.log(foo == !foo);
console.log(foo == foo);
→ true
→ true

8. console.log( 3.toString() )
console.log( 3..toString() )
→ SyntaxError: identifier starts immediately after numeric literal
→ "3"
var a = new Number;
console.log(a == 0)
var a = new String;
console.log(a == "")
var a = new Object;
console.log(a == {})
var a = new Array;
console.log(a == [])
→ true
→ true
→ false
→ false

9. var a = {};
console.log( a == {} );
var a = [];
console.log( a == [] );
→ false
→ false
console.log( (!+[]+[]+![]) );
→ "truefalse"
console.log(
(![]+[])[+[]]+(![]+[])[+!+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+
[])[!+[]+!+[]] )
→ "fail"

10. console.log( {} + {} );
→ NaN
console.log( [] + [] );
→ ""
console.log( [] + {} );
→ "[object Object]"
console.log( {} + [] );
→0
console.log( 1 < 2 < 3 );
console.log( 3 < 2 < 1);
→ true
→ true

11. JavaScript. Just be smarter!

12. Links
WTF JavaScript: http://www.wtfjs.com/
Destroy All Software Screencasts:
http://www.destroyallsoftware.com/
JavaScript Tutorial: http://www.javascript.info/
JavaScript Specification:
http://www.ecma-
international.org/publications/standards/Ecma-
262.htm