截至2016年6月，在最新的Chrome上做了一些测试(2016年5月，浏览器市场份额为71%，并且还在增加):

The fastest loop is a for loop, both with and without caching length delivering really similar performance. (The for loop with cached length sometimes delivered better results than the one without caching, but the difference is almost negligible, which means the engine might be already optimized to favor the standard and probably most straightforward for loop without caching). The while loop with decrements was approximately 1.5 times slower than the for loop. A loop using a callback function (like the standard forEach), was approximately 10 times slower than the for loop.

我相信这个线程太旧了，它误导程序员认为他们需要缓存长度，或者使用反向遍历，同时递减来获得更好的性能，编写的代码不太容易读懂，更容易出错，而不是简单直接的for循环。因此，我建议:

If your app iterates over a lot of items or your loop code is inside a function that is used often, a straightforward for loop is the answer: for (var i = 0; i < arr.length; i++) { // Do stuff with arr[i] or i } If your app doesn't really iterate through lots of items or you just need to do small iterations here and there, using the standard forEach callback or any similar function from your JS library of choice might be more understandable and less prone to errors, since index variable scope is closed and you don't need to use brackets, accessing the array value directly: arr.forEach(function(value, index) { // Do stuff with value or index }); If you really need to scratch a few milliseconds while iterating over billions of rows and the length of your array doesn't change through the process, you might consider caching the length in your for loop. Although I think this is really not necessary nowadays: for (var i = 0, len = arr.length; i < len; i++) { // Do stuff with arr[i] }

http://jsperf.com/caching-array-length/60

我准备的最新版本的test(通过重用旧版本)显示了一件事。

缓存长度并不是那么重要，但也没有坏处。

在Chrome、Opera和Firefox中，在我的Debian Squeeze 64位(我的桌面硬件)中，每次第一次运行上面链接的测试(在新打开的选项卡上)，最后4个片段(图表中的第3、第5、第7和第10)的结果都是最好的。随后的运行给出了完全不同的结果。

性能方面的结论很简单:

使用for循环(向前)并使用!==而不是<进行测试。 如果以后不需要重用数组，那么while循环减去长度和破坏性shift()-ing数组也是有效的。

博士tl;

现在(2011.10)下面的模式看起来是最快的。

for (var i = 0, len = arr.length; i !== len; i++) {
    ...
}

注意缓存。长度在这里并不重要，所以您可以只测试I !== arr。长度和性能不会下降，但是代码会变短。

PS:我知道在snippet with shift()中，它的结果可以用来代替访问第0个元素，但我在重用以前的修订(有错误的while循环)后忽视了这一点，后来我不想失去已经获得的结果。

在使用大多数现代浏览器执行此测试后: https://jsben.ch/wY5fo

目前，最快的循环形式(在我看来也是语法上最明显的)。

具有长度缓存的标准for循环

    var i = 0, len = myArray.length;
    while (i < len) {
        // your code
        i++
    }

我想说，这绝对是我为JavaScript引擎开发者喝彩的地方。运行时应该优化为清晰，而不是聪明。

另一个jsperf.com测试:http://jsperf.com/while-reverse-vs-for-cached-length

反向while循环似乎是最快的。唯一的问题是while(——i)将停止于0。我怎么能访问数组[0]在我的循环那么?

我所知道的最优雅的解决方案是使用地图。

var arr = [1,2,3];
arr.map(function(input){console.log(input);});

截至2016年6月，在最新的Chrome上做了一些测试(2016年5月，浏览器市场份额为71%，并且还在增加):

The fastest loop is a for loop, both with and without caching length delivering really similar performance. (The for loop with cached length sometimes delivered better results than the one without caching, but the difference is almost negligible, which means the engine might be already optimized to favor the standard and probably most straightforward for loop without caching). The while loop with decrements was approximately 1.5 times slower than the for loop. A loop using a callback function (like the standard forEach), was approximately 10 times slower than the for loop.

我相信这个线程太旧了，它误导程序员认为他们需要缓存长度，或者使用反向遍历，同时递减来获得更好的性能，编写的代码不太容易读懂，更容易出错，而不是简单直接的for循环。因此，我建议:

If your app iterates over a lot of items or your loop code is inside a function that is used often, a straightforward for loop is the answer: for (var i = 0; i < arr.length; i++) { // Do stuff with arr[i] or i } If your app doesn't really iterate through lots of items or you just need to do small iterations here and there, using the standard forEach callback or any similar function from your JS library of choice might be more understandable and less prone to errors, since index variable scope is closed and you don't need to use brackets, accessing the array value directly: arr.forEach(function(value, index) { // Do stuff with value or index }); If you really need to scratch a few milliseconds while iterating over billions of rows and the length of your array doesn't change through the process, you might consider caching the length in your for loop. Although I think this is really not necessary nowadays: for (var i = 0, len = arr.length; i < len; i++) { // Do stuff with arr[i] }