问题描述
我偶然发现了这个将 DOM NodeList 转换为常规数组的简洁快捷方式，但我必须承认，我并不完全理解它是如何工作的:
I stumbled onto this neat shortcut for converting a DOM NodeList into a regular array, but I must admit, I don't completely understand how it works:
[].slice.call(document.querySelectorAll('a'), 0)
所以它以一个空数组[] 开始，然后slice 用于将call 的结果转换为一个新数组是吗?
So it starts with an empty array [], then slice is used to convert the result of call to a new array yeah?
我不明白的是call.这如何将 document.querySelectorAll('a') 从 NodeList 转换为常规数组?
The bit I don't understand is the call. How does that convert document.querySelectorAll('a') from a NodeList to a regular array?
推荐答案
这里发生的事情是你调用 slice() 就好像它是 NodeList 的函数一样使用call().slice() 在这种情况下所做的是创建一个空数组，然后遍历它正在运行的对象(最初是一个数组，现在是一个 NodeList)并继续追加元素该对象到它创建的空数组，最终返回.这是一篇文章.
What's happening here is that you call slice() as if it was a function of NodeList using call(). What slice() does in this case is create an empty array, then iterate through the object it's running on (originally an array, now a NodeList) and keep appending the elements of that object to the empty array it created, which is eventually returned. Here's an article on this.
所以它以一个空数组[]开头，然后用slice将调用结果转换为新数组是吗?
这不对.[].slice 返回一个函数对象.一个函数对象有一个函数call()，它调用将call()的第一个参数赋值给this的函数；换句话说，使函数认为它是从参数(document.querySelectorAll('a') 返回的 NodeList)而不是从数组调用的.
That's not right. [].slice returns a function object. A function object has a function call() which calls the function assigning the first parameter of the call() to this; in other words, making the function think that it's being called from the parameter (the NodeList returned by document.querySelectorAll('a')) rather than from an array.
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