JavaScript idiosyncrasies

¯\_(ツ)_/¯

(function(){return`text 'inner'`==`text "inner"`;})();

false

(function(){varobj={valueOf:function(){return3;},toString:function(){return2;},}returnobj+4;})();

7

(function(){varfoo=newObject();varbar=newObject();varmap=newObject();map[foo]='foo';map[bar]='bar';returnmap[foo];})();

"bar"

(function(){returnNaN===NaN;})();

false

(function(){functionfoo(){return'a';}returnfoo();functionfoo(){return'b';}})();

"b"

(function(limit){for(vari=0;i<limit;i++){setTimeout(function(){console.log(i);},0);}})(3);

333

(function(a,b){arguments[1]=3;returnb;})(1,2);

3

(function(a,b,c){deletearguments[0];returnarguments.length;})(1,2,3);

3

(function(){return(function(a,b){}).length;})();

2

(function(a,b){varfoo,bar;foo=(bar=a,b);returnfoo;})(1,2);

2

(function(undefined){varfoo;returnfoo===undefined;})(true);

false

(function(n){return~(n);})(-3);

2

(function(n){return~~n;})(-1.5);

-1

(function(x){return!!x;})('a');

true

(function(){returntypeofnull==='null';})();

false

(function(){return+(newDate())})();

1393812837139

(function(){return(newDate()).valueOf();})();

1393812845834

(function(){return''+(newDate());})();

"Sun Mar 02 2014 18:14:01 GMT-0800 (PST)"

(function(){varfoo='a';(function(foo){foo='b';})(foo);returnfoo;})();

"a"

(function(){returnarguments.toString();})();

"[object Arguments]"

(function(){return(function(){})===(function(){});})();

false

(function(n){returnn===newNumber(n);})(10);

false

(function(x){returnnewString(x)===x;})('a');

false

(function(){return[1+1]===[2];})()

false

(function(){return{foo:'bar'}==={foo:'bar'};})();

false

(function(){for(;;);return1;})();

*Infiniteloop*

(function(){return['10','10','10','10'].map(parseInt);})();

[10,NaN,2,3]

(function(){varo={toString:function(){return'a';},valueOf:function(){return1;}};returno+o;})();

2

(function(){varf=functiong(){return1;};returng();})();

ReferenceError:gisnotdefined

(function(){returnvoid(1+1);})();

undefined

(function(){vara=[1,2];varb=a;a=[1,2];returna===b;})();

false

(function(){varx=1;return(function(){returnx;varx=2;})();})();

undefined

(function(n){vareven=function(num){return(num===0)||!(even(num-1))};var_even=even;even=void0;return_even(n);})(2);

TypeError:undefinedisnotafunction

(function(){varn;functionname(){returnthis.name};n=name.bind({name:'foo'});n=n.bind({name:'bar'})returnn();})();

"foo"

(function(){return('3'>'12')===('03'>'12');})();

false

(function(){returnMath.pow(2,53)===(Math.pow(2,53)+1);}();

true

(function(){returnMath.pow(2,1024)===Infinity;})();

true

(function(){return(Infinity-100)===Infinity;}();

true

(function(){return(0.1+0.2===0.3);})();

false

(function(){return(0.1).toFixed(20);})();

"0.10000000000000000555"

(function(){returnparseFloat('3.3.4');})();

3.3

(function(){return010;})();

8

(function(){return(parseInt('10000000000000000',10)===parseInt('10000000000000001',10));})();

true

(function(n){return(Function)('var n = n || 2; return n;')(n);})(1);

2

vara=1;b=1;(function(){return(deletewindow.a)===(deletewindow.b);})();

false

(function(x){varisMatch,regex=/[\w]/gi;return(regex.test(x)===regex.test(x));})('a');

false

(function(){return![];})();

false

(function(){return+[];})();

0

(function(){return[][[]];})();

undefined

(function(){return+!+[];})();

1

(function(){return[]+[];})();

""

(function(){returntrue+1;})();

2

(function(){return1/'';})();

Infinity

(function(){return1*null;})();

0

(function(){returnnewArray()==false;})();

true

(function(){if([]){return[]==false;}})();

true

(function(){return''.concat(null);})();

"null"

(function(a,b){returna++b;})('a','b');

"aNaN"

(function(){Object.prototype.foo='foo';returnfoo;})();

"foo"

(function(){return1000===1e3;})();

true

(function(){return9999999999999999;})();

10000000000000000

(function(){(function(){vara=b=1;})();returntypeofa===typeofb;})();

false

(function(){returnArray(3).map(function(o){return'a';});})();

[undefined,undefined,undefined]

(function(){varfoo=[0,1,2];foo[10]=10;returnfoo.filter(function(n){returnn===undefined;});})();

[]

(function(x){varret=null;switch(x){case'A':ret='A';break;default:ret='unknown';break;}returnret;})(newString('A'));

"unknown"

(function(){varx={};returnx.prototype===Object.getPrototypeOf(x);})();

false

(function(){functionfoo(){}foo.name='bar';returnfoo.name;})();

"foo"

(function(){returnArray(5).join(',').length;})();

4

(function(x){returnx+++++x;})(2);

6

(function(){'use strict';lettype=typeoffoo;letfoo=1;returntype;})();

ReferenceError:fooisnotdefined

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