有趣的Javascript Array

javascript.array.js

// 先来定义一个数组，并尝试输出其结果
> var a = [1, 2, 3];
> a
[1, 2, 3]

// 目前来看一切正常，没有任何问题
// ok，开始做点有意思的事
> a[-1] = 4;
// 数组发生变化了吗?
> a
[1, 2, 3]
// 没有?
> console.log(a)
[1, 2, 3, -1: 4]
// 多出了一个？尝试另一种输出
> dir(a)
Array(3)
// 看起来仍是长度为3的数组。但是... 如果点开左侧的三角
// 仍旧看到了-1:4
> a.length
3

// 那这个索引(-1)可以访问么？
> a[-1]
4

// 的确可以
// 暂时不管，再来挑战一下极限
> a[NaN] = 5;
> a
[1, 2, 3]

// ( ⊙ o ⊙ )！

// 来真正的挑战一下“极限”
> a[-Infinity] = "P";
> a[-Infinity+3] = "NP";
// 没有报错信息，这也可以
> a[-Infinity] === a[-Infinity+3]
true

// 再来看一下数组a的情况
> console.log(a);
[1, 2, 3, -1: 4, NaN: 5, -Infinity: "NP"]

// 有些混乱了，不妨多输出些信息再来看看
> typeof a
"object"
// 在Javascript的世界里，Array本身就是Object，这没什么值得好奇的
> a.length
3

// ok，继续
> a[function]='err';
SyntaxError: Unexpected token ]

> a[typeof console.log] = "duh";
> a['~'] = '<';
> a[a[typeof a]='huh', void a] = 'puh';
> a[{do: 'break'}] = 'thanks';
> a.continue = ["-",+"you"+"","+"][3,2,1][2];
> a.return = function(p){ return p;};

// 还记得当初的a么?
> a
[1, 2, 3]

// 难道什么都没有发生过么？
> a[a|a] = 3;
> a[-~a&-~a] = 2;
> a[-~-~!a] = 1; 
> a
[3, 2, 1]

// Good, good, nicely reversed
> a['!'-1]
5
// Whoaa? Dude?
> '!'-1
NaN

// Oh yeah, I forgot about that I already have NaN in there
// console.log will reveal other interesting things for sure
> console.log(a);
[  
  -Infinity: "NP",
  0: 3,
  1: 2,
  2: 1,
  -1: 4,
  NaN: 5,
  [object Object]: "thanks",
  continue: "N",
  function: "duh",
  length: 3,
  object: "huh",
  return: function (p){ return p;},
  undefined: "puh",
  ~: "<"
]

// Hmm, there are couple of nice ones 
> a.length = 2;
> a
[3, 2]

// Sorry for that
> a[{}];
"thanks"
> a['[object Object]'] = "you're welcome";

// Also, where did that continue: "N" come from? Was that from example with N=NP?
// Not really... that actually reminds me of one episode from my famous 
// "JavaScript sucks" series:
// You should try this one. Just put the following into your favorite JS console:
// Or are you afraid of JavaScript? :)
> (({}-1)+"")[2]+({}+[])[1]+" "+((~-1<~[0])+"")[1/(1/0)]+((/./>/^/)+"")[4]+(""+!!(3^3))[1]+(""+!!(_="$"))[1]+"!"
// ... result stripped ... I won't make it that easy for you.

// Let's reveal one of the sneaky ones 
// (that has actually nothing to do with arrays):
> a[100] = "Never gonna \
give you up,";
> a[101] = "Never gonna \ 
let you down";
SyntaxError: Unexpected token ILLEGAL

// Wow ... I thing I have been just Rickrolled by Chrome interpreter
// and I thought he would never gonna run around and desert me
// Do you know how this happened? BroTip: Try to copypaste it into your console.

// Talking about Syntax Errors, let's say we need a function that performs
// this importing-like functionality for us. Let's call it import.
> function import() {}
SyntaxError: Unexpected token import




// One thing I haven't tried yet is doing a bit of recursion in array
> a.me = a;
> console.log(a);
[... me: Array[3] ...] // striped other previously messed up things

> console.log(a.me.me.me)
[... me: Array[3] ...]

// If you would run the same thing in Node.JS you would see more explanatory
> console.log(a.me.me.me)
[ me: [Circular] ]

// Let's run simple one liner to try to iterate through recursive object
> for(var i=0, c=a; c=c.me; console.log(i), i++);
0
1
...
26012391
...

// Ok, Node.JS is still running, no simple way to kill it. 
// What about Chrome console?
> for(var i=0, c=a; c=c.me; console.log(i), i++);
0
1
...
314
...
2679
...

// Chrome died. Goodbye a. See you in Silicon Heaven.

// That reminds me of good old times when I tried to view 5MB XML without 
// line breakings in Chrome, Opera, IE, Firefox...

// Let's start chrome console again with clean array
> var a = [];
> a.me = a;
// Hmm I need to add some elem to array, so I can just copypaste that loop again
> a[1] = 2
> a
[undefined × 1, 2]

// That's interesting - array is 'filled up' with undefineds and Chrome
// prints that out neatly
// Let's test how long this loop take
> console.time('evt'); for(var i=0, c=a; c=c.me, i < 10000; console.log(i), i++); console.timeEnd('evt');
evt: 1552.587ms

// Let's try the same thing with object to see if there's any difference
> var o = {};
> o.me = o;
> console.time('evt'); for(var i=0, c=o; c=c.me, i < 10000; console.log(i), i++); console.timeEnd('evt');
evt: 1610.678ms

// Not really - so what to take from this: Arrays are Objects, essentially.
// And yes, proving that by executing console.log multiple times is just
// plain stupid.

// One last interesting thing
> i
10000