JavaScript 中的 forEach 可以返回吗? [英] Can forEach in JavaScript make a return?

问题描述

我想知道 JavaScript 中的 forEach 是否可以返回，这是我的代码:

I wonder if forEach in JavaScript can make a return, here is my code:

var a = [0, 1, 2, 3, 4];

function fn(array) {
  array.forEach(function(item) {
    if (item === 2) return false;
  });

  return true;
}

var ans = fn(a);
console.log(ans); // true

我想知道 2 是否在我的数组中，如果是，则返回 false，但似乎 forEach 函数循环了整个数组并忽略了返回.

I want to find out if 2 is in my array, if so, return false, but it seems that the forEach function has looped the whole array and ignore return.

我想知道是否可以使用 forEach 获得我想要的答案(我知道我可以使用 for(..) 获得我想要的答案)?亲爱的朋友，请帮助我，非常感谢！

I wonder if I can get the answer I want with forEach ( I know I can get what I want using for(..))? dear friend, pls help me, with great thanks!

推荐答案

您可以使用 indexOf 代替 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf

You can use indexOf instead https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf

function fn(array) {
  return (array.indexOf(2) === -1);
}

<小时>

同样来自 forEach 的文档 - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach

注意:除了通过以下方式停止或中断 forEach() 循环抛出异常.如果你需要这样的行为，.forEach()方法是错误的工具，请改用普通循环.

Note: There is no way to stop or break a forEach() loop other than by throwing an exception. If you need such behaviour, the .forEach() method is the wrong tool, use a plain loop instead.

因此，不能以您使用的方式使用返回值.但是，您可以执行 throw (不建议这样做，除非您确实需要在那里引发错误)

So, the return value cannot be used the way you are using it. However you could do a throw (which is not recommended unless you actually need an error to be raised there)

function fn(array) {
  try {
      array.forEach(function(item) {
         if (item === 2) throw "2 found";
      });
  }
  catch (e) {
    return false;
  }

  return true;
}

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