Hacker News: A Javascript journey with only six characters

V2EX = way to explore

V2EX 是一个关于分享和探索的地方

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这是一个创建于 2969 天前的主题，其中的信息可能已经有所发展或是发生改变。

先执行下面的代码 :-)

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8 条回复 • 2016-10-09 22:27:08 +08:00

goofansu

2016-10-09 09:17:38 +08:00 via iPhone

javascript 博大精深啊

shiji

2016-10-09 09:20:58 +08:00

乌云很早就提过，标题是： jother 编码之谜

另外还有一个叫 JSfuck 的，也有类似的功能。

最后附赠一份清单：
http://www.evil0x.com/posts/27318.html

CYKun

2016-10-09 10:18:55 +08:00 via Android

javascript 里类似 []+[]==="" 这样的行为是语言规范定义的吗？是的话不是显得很奇怪吗。。

est

2016-10-09 10:29:22 +08:00

当年在 slackers 上那个神贴一步一步看众大神把字符逐渐精简到 6 字符的路过。

reallarry

2016-10-09 10:53:27 +08:00 via Android

wtf

Havee

2016-10-09 11:43:08 +08:00

每次看到类似的，都觉得很作

noe132

2016-10-09 16:33:49 +08:00

@CYKun
语言规范定义了。
两个值用+操作符，首先要转化成原始值类型，用到里内部函数 ToPrimitive 。
这种情况下对象转化为原始值类型调用对象 toString()方法或 ValueOf()方法。
http://www.ecma-international.org/ecma-262/7.0/index.html#sec-addition-operator-plus

[]的 toString 继承自 Array.prototype.toString ，方法的定义在
http://www.ecma-international.org/ecma-262/7.0/index.html#sec-array.prototype.tostring

Let array be ? ToObject(this value).
Let func be ? Get(array, "join").
If IsCallable(func) is false, let func be the intrinsic function %ObjProto_toString%.
Return ? Call(func, array).

意思就是返回调用 join 方法的值
空数组[].join()的值就是 ""

所以[]+[] === ""在 runtime 时处理的操作就是讲两个空数组转换为原始值类型相加，再与右边比较

CYKun

2016-10-09 22:27:08 +08:00

@noe132 这规范颇有点先打一枪再画靶子的味道 : )