JavaScript的类型自动转换高级玩法JSFuck
0 前言
最开始是不小心在微信公众号（程序员大咖）看到一篇JS的高逼格代码，然后通过里面的链接跳转到了JSFuck的wiki，就像顺着迷宫找宝藏的感觉，感叹JS的自动类型转换的牛逼。
1 样例
(!(~+[])+{})[--[~+""][+[]]*[~+[]] + ~~!+[]]+({}+[])[[~!+[]]*~+[]] //如何装逼用代码骂别人SB
(([][[]]+[])[+!![]]+([]+{})[!+[]+!![]])//如何用代码优雅地证明自己NB
2 原理
1.对于非原始类型的，通过ToPrimitive() 将值转换成原始类型：
ToPrimitive(input, PreferredType?)
可选参数PreferredType是Number或者是String。返回值为任何原始值。如果PreferredType是Number，执行顺序如下：
如果input为primitive，返回
否则，input为Object。调用 obj.valueOf()。如果结果是primitive，返回。
否则，调用obj.toString(). 如果结果是primitive，返回
否则，抛出TypeError
如果 PreferredType是String，步骤2跟3互换，如果PreferredType没有，Date实例被设置成String，其他都是Number
2.通过ToNumber()把值转换成Number
3.通过ToString()把值转化成字符串
第2,3点可以参考 JavaScript的类型自动转换样例集合处
黄金法则
var a = ![] === false; // !后面的字符会被转为换布尔
var b = +[] === 0; // +后面的字符会被转换为数值
var c = []+[]=== ""; // [] 后面跟的字符会被转换为字符串
var g1 = ![]+[] === "false"
var g2 = []+![] === "false"
所以可以通过这些特殊的转换来获得自己想要的数值和字母
Character JSFuck
+ (+(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+[+!+[]]+[+[]]+[+[]])+[])[!+[]+!+[]]
. (+(+!+[]+[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+[!+[]+!+[]]+[+[]])+[])[+!+[]]
0 +[]
1 +!![] or +!+[]
2 !![]+!![] or !+[]+!+[]
3 !![]+!![]+!![] or !+[]+!+[]+!+[]
4 !![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]
5 !![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]
6 !![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]
7 !![]+!![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]
8 !![]+!![]+!![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]
9 !![]+!![]+!![]+!![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]
a (![]+[])[+!+[]]
b ([]+{})[+!+[]+!+[]]
d ([][[]]+[])[!+[]+!+[]]
e (!![]+[])[!+[]+!+[]+!+[]]
f (![]+[])[+[]]
i ([![]]+[][[]])[+!+[]+[+[]]]
I (+(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+(+!+[])+(+[])+(+[])+(+[]))+[])[+[]]
l (![]+[])[!+[]+!+[]]
N (+[![]]+[])[+[]]
n ([][[]]+[])[+!+[]]
r (!+[]+[])[+!+[]]
s (![]+[])[!+[]+!+[]+!+[]]
t (!+[]+[])[+[]]
u ([][[]]+[])[+[]]
y (+[![]]+[+(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+(+!+[])+(+[])+(+[])+(+[]))])[+!+[]+[+[]]]
其它通过以上的基本规则可以拼接出自己想要内容，其它有趣的例子如下：
([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[+[]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+([][[]]+[])[+[]]+([][[]]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[!+[]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]])()([][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[!+[]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]])()(([]+{})[+[]])[+[]]+(!+[]+!![]+!![]+!![]+!![]+!![]+!![]+[])+(!+[]+!![]+!![]+!![]+!![]+!![]+!![]+[]))+([]+{})[+!![]]+(!![]+[])[+!![]]+(![]+[])[!+[]+!![]]+([][[]]+[])[!+[]+!![]]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+([][[]]+[])[+[]]+([][[]]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[!+[]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]])()([][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+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//输出的内容是hello world!
((+(+!![]+(!![]+[])[!![]+!![]+!![]]+(+!![]+[])+(+[]+[])+(+[]+[])+(+[]+[])+[])+[])+[])[+[]]+({}+[])[!![]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!![]+!![]]+({}+[])[+!![]]+[][(![]+[])[!![]+!![]+!![]]+({}+[])[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][({}+[])[!![]+!![]+!![]+!![]+!![]]+({}+[])[+!![]]+({}[[]]+[])[+!![]]+(![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+[]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+({}+[])[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+({}[[]]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]+!![]+!![]]+({}[[]]+[])[+[]]+({}[[]]+[])[+!![]]+(!![]+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(![]+[])[+!![]]+([]+[][(![]+[])[!![]+!![]+!![]]+({}+[])[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][({}+[])[!![]+!![]+!![]+!![]+!![]]+({}+[])[+!![]]+({}[[]]+[])[+!![]]+(![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+[]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+({}+[])[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+({}[[]]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!![]+!![]]+({}+[])[+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(![]+[])[+!![]]+(!![]+[])[+[]]+({}[[]]+[])[!![]+!![]+!![]+!![]+!![]]+({}+[])[+!![]]+({}[[]]+[])[+!![]])())[!![]+!![]+!![]]+(!![]+[])[!![]+!![]+!![]])()([][(![]+[])[!![]+!![]+!![]]+({}+[])[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][({}+[])[!![]+!![]+!![]+!![]+!![]]+({}+[])[+!![]]+({}[[]]+[])[+!![]]+(![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+[]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+({}+[])[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+({}[[]]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]+!![]+!![]]+(!![]+[])[!![]+!![]+!![]]+(![]+[])[!![]+!![]+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(![]+[])[+!![]]+([]+[][(![]+[])[!![]+!![]+!![]]+({}+[])[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][({}+[])[!![]+!![]+!![]+!![]+!![]]+({}+[])[+!![]]+({}[[]]+[])[+!![]]+(![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+[]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+({}+[])[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+(!![]+[])[!![]+!![]+!![]]+(!![]+[])[+[]]+({}[[]]+[])[+[]]+(!![]+[])[+!![]]+({}[[]]+[])[+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!![]+!![]]+({}+[])[+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]]+(![]+[])[+!![]]+(!![]+[])[+[]]+({}[[]]+[])[!![]+!![]+!![]+!![]+!![]]+({}+[])[+!![]]+({}[[]]+[])[+!![]])())[!![]+!![]+!![]]+(!![]+[])[!![]+!![]+!![]])()(({}+[])[+[]])[+[]]+(!![]+!![]+!![]+!![]+!![]+!![]+!![]+[])+(!![]+!![]+!![]+!![]+!![]+!![]+[]))+(!![]+[])[!![]+!![]+!![]]+({}+[])[!![]+!![]+!![]+!![]+!![]+!![]+!![]]+((+(+!![]+(!![]+[])[!![]+!![]+!![]]+(+!![]+[])+(+[]+[])+(+[]+[])+(+[]+[])+[])+[])+[])[!![]+!![]+!![]+!![]+!![]+!![]+!![]]+({}+[])[+!![]]+({}[[]]+[])[+[]]
//I love you
3.分析样例中的NB，SB分析可见参考资料3
(([][[]]+[])[+!![]]+([]+{})[!+[]+!![]])
//首先先拆解
([][[]]+[])[+!![]] + ([]+{})[!+[]+!![]])
//左边部分解析
([][[]]+[])[+!![]] -> [][[]]+[] 和 +!![]
[][[]]+[] ->[][[]] + []
//[][[]]+[]
[[]],[]是数组的下标，转换成数字时0，等价于[0].
[][[]]是一个空的数组，长度为零，取第一个长度即[][0],得到的值是undefined
当undefined+[], []会被转换成""，然后就变成了“undefined”
所以[][[]]+[] 为“undefined”
//+!![]
![],根据黄金法则，然后![] 为false，!![]为true,+!![]则被转换为数字1
所以([][[]]+[])[+!![]] 等价于“undefined”[1] 为n
//右边部分解析
([]+{})[!+[]+!![]]) ->[]+{}和!+[]+!![]]
//[]+{}
{} 等价于new Object(), [] + 对象，[]会转换成""，然后结果为"[object Object]"
//!+[]+!![]
查询上表，可以知道!+[]和!![]都是1，所以!+[]+!![]就是2了。
所以"[object Object]".[2]='b'
4.更神奇的样例
//数字0的两种表示
+[] //0;
+![] // 0; //第二种
!"" //true，""转换成boolean值是false
![] //false，[], 空数组也是对象的，转换为布尔值是true
[] == "" //true，同时转换成数字0 //第三种
{}+[] //0
({}+[]) //"[object Object]"
[]+{} //"[object Object]" //"false"的各种写法
[]+!{}
!{}+[]
[]+![]
![]+[] //sb的常规写法
(![]+{})[+!![]+!![]+!![]]+([]+{})[+!![]+!![]]
(![]+[])[!+[]+!+[]+!+[]]+([]+{})[+!+[]+!+[]] //nb的常规写法
([][[]]+[])[+!![]]+([]+{})[+!![]+!![]]
([][[]]+[])[+!+[]]+([]+{})[+!+[]+!+[]] //1的各种写法
+!+![]
+!+[]
+!![]
+!+!{}
+!+{}
+!!{}
5 参考
1.http://mp.weixin.qq.com/s/4HpQxQF2_CLh5VL3_ijbQQ
2. js奇淫技巧1
4.https://en.wikipedia.org/wiki/JSFuck
6.https://github.com/aemkei/jsfuck/blob/master/jsfuck.js
7.在线生成网站: http://tmxk.org/jother/
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