关于JavaScript的切片和拼接方法的问题 [英] A question about JavaScript's slice and splice methods

问题描述

我碰到下面的code来了：

I came across the following code:

var f = function () {
    var args = Array.prototype.slice.call(arguments).splice(1);

    // some more code 
};

基本上，结果 ARGS 是一个数组，它是的复制参没有它的第一个元素。

Basically, the result in args is an array that is a copy of the arguments without its first element.

但我不明白到底是为什么的˚F 参数（这是保存一个对象该函数的输入参数为一个阵列状物体）对象被传递到片方法，以及如何片（1）被移除第一元件（定位在索引0）

But what I can't understand exactly is why f's arguments (which is an object that holds the function's inputted arguments into an array-like object) object is being passed to the slice method and how slice(1) is removing the first element (positioned at index 0).

任何人都可以请解释一下吗？

Can anyone please explain it for me?

的 P.S。在code是这个<一个href=\"http://stackoverflow.com/questions/373157/how-can-i-pass-a-reference-to-a-function-with-parameters\">partial应用功能 的

推荐答案

＆LT;注意>

从实际的code <一个href=\"http://stackoverflow.com/questions/321113/how-can-i-$p$p-set-arguments-in-javascript-function-call-partial-function-applic/321527#321527\">linked答案是：

var args = Array.prototype.slice.call(arguments, 1);

即。 切片，而不是拼接

＆LT; /注>

i.e. "slice", not "splice"
</Note>

首先，在片方法经常被用来的使数组这就是所谓的副本：

First of all, the slice method is often used to make a copy of the array it's called on:

var a = ['a', 'b', 'c'];
var b = a.slice();  // b is now a copy of a
var c = a.slice(1); // c is now ['b', 'c']

所以，简单的答案是，code基本上是模仿：

So the short answer is that the code is basically emulating:

arguments.slice(1); // discard 1st argument, gimme the rest

但是你不能直接这样做。在<一个href=\"https://developer.mozilla.org/en/JavaScript/Reference/Functions_and_function_scope/arguments\">special 参数对象（可用的所有JavaScript函数执行上下文中），但基于阵列的如的，它通过支持索引 [] 运营商，数字键，实际上不是一个数组;你不能 .push 到它， .pop 关闭，或 .slice 它，等等。

However you can't do that directly. The special arguments object (available inside the execution context of all JavaScript functions), although Array-like in that it supports indexing via the [] operator with numeric keys, is not actually an Array; You can't .push onto it, .pop off it, or .slice it, etc.

在code实现这一点的方法是欺骗的片功能（这又是不提供参数对象）来运行的在的参数，通过<一个上下文href=\"https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/call\"><$c$c>Function.prototype.call:

The way the code accomplishes this is by "tricking" the slice function (which again is not available on the arguments object) to run in the context of arguments, via Function.prototype.call:

Array.prototype.slice // get a reference to the slice method
                      // available on all Arrays, then...
  .call(              // call it, ...
    arguments,        // making "this" point to arguments inside slice, and...
    1                 // pass 1 to slice as the first argument
  )

Array.prototype.slice.call（参数）.splice（1）完成同样的事情，但使外来调用拼接（ 1），其中删除的从数组元素从 Array.prototype.slice.call（参数）开始返回首页 1 ，并继续到数组的结尾。 拼接（1）在IE无法正常工作（它在技术上缺少第二个参数告诉它有多少项目来删除IE浏览器和ECMAScript需要）。

Array.prototype.slice.call(arguments).splice(1) accomplishes the same thing, but makes an extraneous call to splice(1), which removes elements from the array returned from Array.prototype.slice.call(arguments) starting at index 1 and continuing to the end of the array. splice(1) doesn't work in IE (it's technically missing a 2nd parameter telling it how many items to remove that IE and ECMAScript require).

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