Function.call方法作为回调 [英] Function.call method as callback

问题描述

对不起，如果我错过了一些东西，但当我尝试使用call方法作为回调时，它会在Chrome和Node.js中给出奇怪的错误。

Excuse me if I've something missed, but when I try to use call method as a callback it gives me strange error in both Chrome and Node.js.

['  foo', ' bar  '].map(String.prototype.trim.call);
TypeError: ["  foo", " bar  "].map is not a function
at Array.map (native)

但这些片段有效：

['  foo', ' bar  '].map(function (item) { 
    return String.prototype.trim.call(item);
}); // => ['foo', 'bar']
/*
  and ES2015
*/
['  foo', ' bar  '].map(function () { 
    return String.prototype.trim.call(...arguments);
}); // => ['foo', 'bar']

此外我还检查了 call function：

Also I've checked type of call function:

typeof String.prototype.trim.call; // => 'function'

我做错了什么？谁能解释一下为什么我会收到这样的错误？谢谢。

Am I doing something wrong? Could anyone please explain me why I get such error? Thanks.

推荐答案

解决问题的最简单方法就是写出来：

The easiest solution to your problem is to just write it out:

['  foo', ' bar  '].map(s => s.trim());

如果你想传递一个函数，你需要一些比你想要的更复杂的东西，沿着这条线of

If you want to pass a function, you will need something more complicated than you want, along the lines of

.map(Function.call.bind(String.prototype.trim))

或者如果您愿意

.map(Function.call, String.prototype.trim)

此问题可能会回答您的所有问题。

This question may answer all your issues.

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