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见 http://h.acfun.tv/t/4240594?r=4256785 |
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// 要注意 JS 里,closure 的值的确是有些奇怪的地方,像这样写就会出问题: | |
function mkClosures() { | |
var xs = []; | |
for (var i = 0; i < 10; ++i) { | |
xs.push(function() { console.log(i); }); | |
} | |
return xs; | |
} | |
var cs = mkClosures(); | |
for (var i = 0; i < cs.length; ++i) { | |
cs[i](); | |
} | |
// 看起来会 log 出 0-9,但是实际上都是 10。你可以认为 closure 里存着的是同一个 i。 | |
// | |
// 那么怎么办呢?你可以这么写: | |
function mkClosure(i) { | |
return function() { | |
console.log(i); | |
} | |
} | |
function mkClosures() { | |
var xs = []; | |
for (var i = 0; i < 10; ++i) { | |
xs.push(mkClosure(i)); | |
} | |
return xs; | |
} | |
var cs = mkClosures(); | |
for (var i = 0; i < cs.length; ++i) { | |
cs[i](); | |
} |
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