0 前言

最開始是不小心在微信公眾號（程序員大咖）看到一篇JS的高逼格代碼，然後通過裏面的鏈接跳轉到了JSFuck的wiki，就像順著迷宮找寶藏的感覺，感嘆JS的自動類型轉換的牛逼。

1 樣例

(!(~+[])+{})[--[~+""][+[]]*[~+[]] + ~~!+[]]+({}+[])[[~!+[]]*~+[]] //如何裝逼用代碼罵別人SB
(([][[]]+[])[+!![]]+([]+{})[!+[]+!![]])//如何用代碼優雅地證明自己NB

2 原理

1.對於非原始類型的，通過ToPrimitive() 將值轉換成原始類型：

　　ToPrimitive(input, PreferredType?)

　　可選參數PreferredType是Number或者是String。返回值為任何原始值。如果PreferredType是Number，執行順序如下：

　　如果input為primitive，返回

　　否則，input為Object。調用 obj.valueOf()。如果結果是primitive，返回。

　　否則，調用obj.toString(). 如果結果是primitive，返回

　　否則，拋出TypeError

　　如果 PreferredType是String，步驟2跟3互換，如果PreferredType沒有，Date實例被設置成String，其他都是Number

2.通過ToNumber()把值轉換成Number

3.通過ToString()把值轉化成字符串

第2,3點可以參考 JavaScript的類型自動轉換樣例集合處

所以可以通過這些特殊的轉換來獲得自己想要的數值和字母

Character	JSFuck
+	(+(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+[+!+[]]+[+[]]+[+[]])+[])[!+[]+!+[]]
.	(+(+!+[]+[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+[!+[]+!+[]]+[+[]])+[])[+!+[]]
0	+[]
1	+!![] or +!+[]
2	!![]+!![] or !+[]+!+[]
3	!![]+!![]+!![] or !+[]+!+[]+!+[]
4	!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]
5	!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]
6	!![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]
7	!![]+!![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]
8	!![]+!![]+!![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]
9	!![]+!![]+!![]+!![]+!![]+!![]+!![]+!![]+!![] or !+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]
a	(![]+[])[+!+[]]
d	([][[]]+[])[!+[]+!+[]]
e	(!![]+[])[!+[]+!+[]+!+[]]
f	(![]+[])[+[]]
i	([![]]+[][[]])[+!+[]+[+[]]]
I	(+(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+(+!+[])+(+[])+(+[])+(+[]))+[])[+[]]
l	(![]+[])[!+[]+!+[]]
N	(+[![]]+[])[+[]]
n	([][[]]+[])[+!+[]]
r	(!+[]+[])[+!+[]]
s	(![]+[])[!+[]+!+[]+!+[]]
t	(!+[]+[])[+[]]
u	([][[]]+[])[+[]]
y	(+[![]]+[+(+!+[]+(!+[]+[])[!+[]+!+[]+!+[]]+(+!+[])+(+[])+(+[])+(+[]))])[+!+[]+[+[]]]

其它通過以上的基本規則可以拼接出自己想要內容，其它有去的例子如下：

([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[+[]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+([][[]]+[])[+[]]+([][[]]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[!+[]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]])()([][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[!+[]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]])()(([]+{})[+[]])[+[]]+(!+[]+!![]+!![]+!![]+!![]+!![]+!![]+[])+(!+[]+!![]+!![]+!![]+!![]+!![]+!![]+[]))+([]+{})[+!![]]+(!![]+[])[+!![]]+(![]+[])[!+[]+!![]]+([][[]]+[])[!+[]+!![]]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+([][[]]+[])[+[]]+([][[]]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[!+[]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]])()([][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(![]+[])[!+[]+!![]+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+([]+[][(![]+[])[!+[]+!![]+!![]]+([]+{})[+!![]]+(!![]+[])[+!![]]+(!![]+[])[+[]]][([]+{})[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]]+(![]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+[]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(!![]+[])[+[]]+([]+{})[+!![]]+(!![]+[])[+!![]]]((!![]+[])[+!![]]+([][[]]+[])[!+[]+!![]+!![]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!![]]+([][[]]+[])[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]+!![]+!![]]+(![]+[])[!+[]+!![]]+([]+{})[+!![]]+([]+{})[!+[]+!![]+!![]+!![]+!![]]+(+{}+[])[+!![]]+(!![]+[])[+[]]+([][[]]+[])[!+[]+!![]+!![]+!![]+!![]]+([]+{})[+!![]]+([][[]]+[])[+!![]])())[!+[]+!![]+!![]]+([][[]]+[])[!+[]+!![]+!![]])()(([]+{})[+[]])[+[]]+(!+[]+!![]+[])+(+!![]+[]))
//輸出的內容是hello world!

3.分析樣例中的NB，SB分析可見參考資料3　　

(([][[]]+[])[+!![]]+([]+{})[!+[]+!![]])
//首先先拆解
([][[]]+[])[+!![]]   +   ([]+{})[!+[]+!![]])
//左邊部分解析
 ([][[]]+[])[+!![]] -> [][[]]+[] 和 +!![]
[][[]]+[] ->[][[]]  +   [] 

//[][[]]+[]
[[]],[]是數組的下標，轉換成數字時0，等價於[0].
[][[]]是一個空的數組，長度為零，取第一個長度即[][0],得到的值是undefined
當undefined+[], []會被轉換成""，然後就變成了“undefined”
所以[][[]]+[] 為“undefined”
//+!![]
![],[]被轉換成""，然後![] 為false，!![]為true,+!![]則被轉換為數字1
所以([][[]]+[])[+!![]] 等價於“undefined”[1] 為n

//右邊部分解析
([]+{})[!+[]+!![]]) ->[]+{}和!+[]+!![]]
//[]+{}
{} 等價於new Object(), [] + 對象，[]會轉換成“”，然後結果為"[object Object]"
//!+[]+!![]
查詢上表，可以知道!+[]和!![]都是1，所以!+[]+!![]就是2了。
所以"[object Object]".[2]=‘b‘　　　

4.更神奇的樣例

//數字0的兩種表示
+[] //0;
+![] // 0;

//第二種
!"" //true，""轉換成boolean值是false
![] //false，[], 空數組也是對象的，轉換為布爾值是true
[] == "" //true，同時轉換成數字0

5 參考

1. http://mp.weixin.qq.com/s/4HpQxQF2_CLh5VL3_ijbQQ

2. js奇淫技巧1

3. 一行能裝逼的JavaScript代碼

4.https://en.wikipedia.org/wiki/JSFuck

JavaScript的類型自動轉換高級玩法JSFuck