我不确定这行
javascript中发生了什么：
- alert( (''+[][[]])[!+[]+!+[]] ); // shows "d"
我发现了什么：
- var a = ! + []; // == true
- var b = ! + [] + ! + []; // == 2
似乎第二部分是对一系列字母或某种类型的引用,但我不明白它是如何产生的
- (''+[][[]])
也：
- alert( (''+[][])[2] ); // nothing happens; console says "unexpected token ]"
- alert( (''+[[]][])[2] ); // nothing happens; console says "unexpected token ]"
- alert( (''+[[]][[]])[2] ); // shows "d"
- alert( (""+true)[2] ); // shows "u"
解决方法
我会为你分解它：
- ('' + [][[]])[!+[]+!+[]]
- = ('' + undefined)[!+[]+!+[]] // [][[]] grabs the []th index of an empty array.
- = 'undefined'[! + [] + ! + []]
- = 'undefined'[(! + []) + (! + [])]
- = 'undefined'[true + true]
- = 'undefined'[2]
- = 'd'
！ [] == true在这里解释What’s the significant use of unary plus and minus operators?
