for-in vs Object.key forEach没有继承属性 [英] for-in vs Object.key forEach without inherited properties

问题描述

我正在寻找 Object.keys + forEach vs 的性能指标-in 包含普通对象。

I was looking at a perf benchmark of Object.keys + forEach vs for-in with normal objects.

这个基准测试显示 Object.keys + forEach 是<强>比 for-in 方法慢<62％。但是，如果您不想获取继承的属性，该怎么办？ for-in 包含所有非本地继承对象，因此我们必须使用 hasOwnProperty 进行检查。

This benchmark shows that Object.keys + forEach is 62% slower than the for-in approach. But what if you don't want to get the inherited properties? for-in includes all non-native inherited objects, so we'll have to use hasOwnProperty to check.

我试图在这里制作另一个 基准 正是这样做的。但现在 for-in 方法比 Object.keys + <慢41％ code> forEach 。

I tried to make another benchmark here doing exactly that. But now the for-in approach is 41% slower than Object.keys + forEach.

update

上述测试是在Chrome中完成的。再次测试它但是我得到了不同的结果： Object.keys（..）。forEach（..）慢34％，奇数。

The above test was done in Chrome. Tested it again but with Safari and I'm getting different results: Object.keys(..).forEach(..) 34% slower, odd.

注意：我进行基准测试的原因是检查它与 Node.js 的关系。

问题：

• 是 jsperf Chrome 的结果相当于 Node.js ？


• 发生了什么，为什么单个条件使 for-in 接近慢41％比 Object.keys Chrome 中的+ forEach ？

• Are the jsperf result for Chrome considerable for Node.js?
• What happened, how come a single conditional made the for-in approach 41% slower than Object.keys + forEach in Chrome?

推荐答案

node.js使用V8，虽然我猜它与Chrome中的当前版本不一样，但我想这是节点在该主题上表现的一个很好的指标。

node.js uses V8, although I guess it's not the same as the current version in Chrome, but I guess it's a good indicator of node's performances on the subject.

其次，你正在使用 forEach ，这在开发时非常方便，但每次迭代都会添加一个回调，这是一个（相对）长度任务。所以，如果你对表演感兴趣，你为什么不用正常的进行循环？

Secondarily, you're using forEach, which is quite handy when developing but adds a callback for every iteration, and that's a (relatively) lenghty task. So, if you're interested in performances, why don't you just use a normal for loop?

for (var i = 0, keys = Object.keys(object); i < keys.length; i++) {
    // ...
}

这样可以获得最佳性能，也可以解决Safari中的速度问题。

This yields the best performances you can get, solving your speed problems in Safari too.

简而言之：它不是有条件的，而是对 hasOwnProperty 的调用会产生影响。你在每次迭代时都在进行函数调用，这就是为什么 for ... in 变慢了。

In short: it's not the conditional, it's the call to hasOwnProperty that makes a difference. You're doing a function call at every iteration, so that's why for...in becomes slower.

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