为什么任何对象原型都不能用作forEach回调? [英] Why doesn't any object prototype work as a forEach callback?

问题描述

我只是想让它成为一个挑战，但还没有找到答案，而不是一个问题.

Rather than a question, I just wanted it to be a challenge but couldn't find an answer yet.

例如，我们有一个字符串数组

For example, we have an array of strings

x = ['a', '   b', '  c  ']

，我想修剪所有元素.我尝试了apply和call方法，但均未按预期工作:

and I want to trim all the elements. I tried apply and call methods but neither worked as expected:

x.forEach(String.prototype.trim.call)
// Uncaught TypeError: undefined is not a function

x.forEach(String.prototype.trim.apply)
// Uncaught TypeError: Function.prototype.apply was called on undefined, which is a undefined and not a function

这是怎么回事? apply/call应该从每个函数的第一个参数开始，一切似乎都很好.

What's going on here? apply/call should take their first argument from for each function and everything seems fine.

推荐答案

尝试一下，

x = ['a', '   b', '  c  ']
x.map(function(item) { return item.trim() })

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