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?
