试试这个:

var myarray =[],
i = myarray.lenght;
while(i--){
// do somthing
}

截至2017年9月，这些jsperf测试显示以下模式在Chrome 60上性能最佳:

function foo(x) {
 x;
};
arr.forEach(foo);

有人能繁殖吗?

**缓存数组的长度在循环内，一些秒的时间将被规避。取决于数组中的项，如果数组中有更多项，则时间毫秒有很大差异*

**

sArr; //Array[158];

for(var i = 0 ; i <sArr.length ; i++) {
 callArray(sArr[i]); //function call
}

***end: 6.875ms***

**

**

sArr; //Array[158];
for(var i = 0,len = sArr.length ; i < len ; i++) {
  callArray(sArr[i]); //function call
}

***end: 1.354ms***

**

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);});

现在是2022年底

有时根本没有用数组长度计算:

如果你有一个索引为var myArray =[1,2,3,4,25,99999999999999]的数组，使用任何索引为1的槽数组(包括forEach)的解决方案都是非常缓慢的。

对我来说，最好的解决方案是:

for(let _i in myArray ) {
   if(myArray[_i]) {
     (function(s) {
        ///
     })(myArray[_i]) 
   }
}

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] }