短路 Array.forEach 就像调用 break [英] Short circuit Array.forEach like calling break

问题描述

[1,2,3].forEach(function(el) {
    if(el === 1) break;
});

我如何使用 JavaScript 中的新 forEach 方法来实现这一点?我试过 return;、return false; 和 break.break 崩溃，return 除了继续迭代什么都不做.

How can I do this using the new forEach method in JavaScript? I've tried return;, return false; and break. break crashes and return does nothing but continue iteration.

推荐答案

forEach 没有内置的 break 功能.要中断执行，您必须抛出某种异常.例如.

There's no built-in ability to break in forEach. To interrupt execution you would have to throw an exception of some sort. eg.

var BreakException = {};

try {
  [1, 2, 3].forEach(function(el) {
    console.log(el);
    if (el === 2) throw BreakException;
  });
} catch (e) {
  if (e !== BreakException) throw e;
}

JavaScript 异常并不是非常漂亮.如果您确实需要在其中 break 循环，则传统的 for 循环可能更合适.

JavaScript exceptions aren't terribly pretty. A traditional for loop might be more appropriate if you really need to break inside it.

改为使用 Array#some:

[1, 2, 3].some(function(el) {
  console.log(el);
  return el === 2;
});

这是有效的，因为只要以数组顺序执行的任何回调返回 true，some 就会返回 true，从而短路执行其余部分.

This works because some returns true as soon as any of the callbacks, executed in array order, return true, short-circuiting the execution of the rest.

some，它的逆every(将在 return false 处停止)和 forEach 都是 ECMAScript 第五版方法，需要添加到 Array.prototype 在缺少它们的浏览器上.

some, its inverse every (which will stop on a return false), and forEach are all ECMAScript Fifth Edition methods which will need to be added to the Array.prototype on browsers where they're missing.

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