JavaScript中，Node.js的：是Array.forEach异步？ [英] JavaScript, Node.js: is Array.forEach asynchronous?

问题描述

我有一个关于本地 Array.forEach JavaScript实现的一个问题：它是否表现异步？
例如，如果我称之为：

I have a question regarding the native Array.forEach implementation of JavaScript: Does it behave asynchronously? For example, if I call:

[many many elements].forEach(function () {lots of work to do})

这会不会是非阻塞？

Will this be non-blocking?

推荐答案

没有，它阻止。看看算法的规范。

No, it is blocking. Have a look at the specification of the algorithm.

然而一个也许更容易理解的实现是在<一个给定的href=\"https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach\">MDN:

However a maybe easier to understand implementation is given on MDN:

if (!Array.prototype.forEach)
{
  Array.prototype.forEach = function(fun /*, thisp */)
  {
    "use strict";

    if (this === void 0 || this === null)
      throw new TypeError();

    var t = Object(this);
    var len = t.length >>> 0;
    if (typeof fun !== "function")
      throw new TypeError();

    var thisp = arguments[1];
    for (var i = 0; i < len; i++)
    {
      if (i in t)
        fun.call(thisp, t[i], i, t);
    }
  };
}

---

如果您需要执行很多code的每个元素，你应该考虑使用不同的方法：

---

If you have to execute a lot of code for each element, you should consider to use a different approach:

function processArray(items, process) {
    var todo = items.concat();

    setTimeout(function() {
        process(todo.shift());
        if(todo.length > 0) {
            setTimeout(arguments.callee, 25);
        }
    }, 25);
}

，然后调用它：

processArray([many many elements], function () {lots of work to do});

这是非阻塞即可。这个例子是从拍摄的高性能的JavaScript 的。

This would be non-blocking then. The example is taken from High Performance JavaScript.

另一种选择可能是的网络工作者的。

Another option might be web workers.

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