Javascript:转发采用可变数量参数的函数调用 [英] Javascript: Forwarding function calls that take variable number of arguments

问题描述

我想我需要像 ruby​​ 的 splat * 之类的东西.

I think I need something like ruby's splat * here.

function foo() {
  var result = '';
  for (var i = 0; i < arguments.length; i++) {
    result += arguments[i];
  }
  return result;
}

function bar() {
  return foo(arguments) // this line doesn't work as I expect
}

bar(1, 2, 3);

我希望它返回 "123"，但我得到的是 "[object Arguments]".我想这是有道理的.它传递的是代表参数的对象，而不是单独的参数.

I want this to return "123", but instead I get "[object Arguments]". Which makes sense, I suppose. It's passing the object that represents the arguments, but not the arguments individually.

那么我如何简单地将任意数量的参数转发给另一个接受任意数量参数的函数?

So how do I simply forward any number of arguments to another function that takes any number of arguments?

推荐答案

更新: 从 ES6 开始，您可以使用 扩展语法来调用函数，将可迭代对象的元素应用为函数调用:

UPDATE: Since ES6, you can use the spread syntax to call a function, applying the elements of an iterable object as argument values of the function call:

function bar() {
  return foo(...arguments);
}

请注意，您还可以接收可变数量的参数作为实际数组，而不是使用 arguments 对象.

Note that you can also receive a variable number of arguments as a real array, instead of using the arguments object.

例如:

function sum(...args) { //  args is an array
  return args.reduce((total, num) => total + num)
}

function bar(...args) {
  return sum(...args) // this just forwards the call spreading the argument values
}

console.log(bar(1, 2, 3)); // 6

在 ES3/ES5 时代，要将参数正确传递给另一个函数，您需要使用 申请:

In the days of ES3/ES5, to correctly pass the arguments to another function, you needed to use apply:

function bar() {
  return foo.apply(null, arguments);
}

apply 方法有两个参数，第一个是thisObj，它的值将用作this被调用的函数，如果使用null或undefined，函数内部的this值将引用全局对象，在非严格模式下，否则为 undefined.

The apply method takes two parameters, the first is the thisObj, the value of it will be used as the this value inside the invoked function, if you use null or undefined, the this value inside the function will refer to the global object, in non-strict mode, otherwise is undefined.

apply 期望的第二个参数是一个类似数组的对象，其中包含要应用于函数的参数值.

The second argument that apply expects is an array-like object that contains the argument values to be applied to the function.

在此处检查上述示例.

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