javascript es6：用例解析rest参数 [英] javascript es6: use case for destructuring rest parameter

问题描述

我刚刚在MDN中看到了一个代码片段，关于如何解析其余参数：

I just saw a code snippet in MDN about destructuring rest parameters like so:

function f(...[a, b, c]) {
  return a + b + c;
}

f(1)          // NaN (b and c are undefined)
f(1, 2, 3)    // 6
f(1, 2, 3, 4) // 6 (the fourth parameter is not destructured)

此页面中的代码段： https://developer.mozilla.org/en- US / docs / Web / JavaScript / Reference / Functions / rest_parameters

虽然休息参数的常见用例对我来说非常清楚（ function foo（... params）{/ * code * /} ）我无法考虑使用其他参数的真实世界用例，就像该代码段中提供的方式一样。相反，我认为在这种情况下，我应该使用一个通用的函数定义：

Although the common use case for rest parameters is very clear to me (function foo(...params){/*code*/}) I could not think about a real world use case to use rest parameters like the way presented in that code snippet. Instead, I think that in that case, I should just use a common function definition:

function f(a, b, c) {
  return a + b + c;
}

f(1)          // NaN (b and c are undefined)
f(1, 2, 3)    // 6
f(1, 2, 3, 4) // 6 (the fourth parameter is not defined)

推荐答案

您的函数f（a，b，c）{...} 确实是写这个的正确方法。它和其余+解构语法之间的唯一区别是，rest参数不会添加到参数个数，即 f.length == 0 。

Your function f(a, b, c) { … } is indeed the proper way to write this. The only difference between that and the rest+destructuring syntax is that rest parameters do not add to number of parameters, i.e. f.length == 0.

将数组解构模式作为rest参数的目标确实没有好的用例。仅仅因为语法允许它并不意味着它在某个地方很有用。 MDN示例可能应该更清楚。

There really is no good use case for putting an array destructuring pattern as the target of a rest parameter. Just because the syntax allows it doesn't mean that it's useful somewhere. The MDN example probably should've made that more clear.

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