javascript - 使用默认值初始化数组

Question

我正在查看this answer我偶然发现需要 Array.apply 来填充数组:

var array = Array.apply(null, Array(5)).map(function() { return 0; });

我已经检查过，这实际上不起作用:

var array = Array(5).map(function() { return 0; });

我知道我能做到

var array = Array(5).fill(0);

为了获得与第一种方法相同的结果，我只是想知道为什么它需要以 null 作为参数的 Array.apply 。

Answer 1

Apply.apply(thisArg, [argsArray])有两个参数

thisArg

The value of this provided for the call to fun. Note that this may not be the actual value seen by the method: if the method is a function in non-strict mode code, null and undefined will be replaced with the global object, and primitive values will be boxed.

argsArray

An array-like object, specifying the arguments with which fun should be called, or null or undefined if no arguments should be provided to the function.

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