Object.keys()的复杂性? [英] Object.keys() complexity?
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问题描述
有人知道常见实现中ECMAScript5的Object.keys()的时间复杂性吗? n
键是 O(n)
吗?时间是否与哈希表的大小成正比(假设使用哈希实现?)?
Anyone know the time-complexity of ECMAScript5's Object.keys() in common implementations? Is it O(n)
for n
keys? Is time proportional to the size of the hash table, assuming a hash implementation?
我正在寻找语言实现者的保证还是现实世界中的基准测试。
I'm looking for either guarantees by language implementors or some real world benchmarking.
推荐答案
在V8中,它似乎是 O(n)
(chrome,节点。 js)至少:
It appears to be O(n)
in V8 (chrome, node.js) at least:
> var hash = {}
> , c = 0;
>
> var s = +new Date();Object.keys(hash);console.log(+new Date() - s);
0
> for(var i=0; i<100000; i++, c++){ hash[c] = 1; }
> var s = +new Date();Object.keys(hash);console.log(+new Date() - s);
26
> for(var i=0; i<100000; i++, c++){ hash[c] = 1; }
> var s = +new Date();Object.keys(hash);console.log(+new Date() - s);
49
> for(var i=0; i<100000; i++, c++){ hash[c] = 1; }
> var s = +new Date();Object.keys(hash);console.log(+new Date() - s);
75
> for(var i=0; i<100000; i++, c++){ hash[c] = 1; }
> var s = +new Date();Object.keys(hash);console.log(+new Date() - s);
102
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