传递比函数声明更多的参数是不是很糟糕？

问题描述

我有一个函数

function callback(obj){...}

是否可以传入比函数签名中声明的更多的对象？ 例如这样称呼：

Is it okay to pass in more objects than were declared in the function signature? e.g. call it like this:

callback(theObject, extraParam);

我在Firefox上尝试过它并没有出现问题，但是它不好要做到这一点？

I tried it out on Firefox and it didn't seem to have a problem, but is it bad to do this?

推荐答案

JavaScript允许这样做，你可以将任意数量的参数传递给函数。

JavaScript allows this, you can pass any arbitrary number of arguments to a function.

可以在 object，它是一个类数组的对象，其数字属性包含调用函数时使用的参数值， length 属性，它告诉你调用也使用了多少个参数，以及被调用者属性，它是对函数本身的引用，例如你可写：

They are accessible in the arguments object which is an array-like object that has numeric properties containing the values of the arguments that were used when the function was invoked, a length property that tells you how many arguments have been used on the invocation also, and a callee property which is a reference to the function itself, for example you could write:

function sum(/*arg1, arg2, ... , argN  */) { // no arguments defined
  var i, result = 0;
  for (i = 0; i < arguments.length; i++) {
    result += arguments[i];
  }
  return result;
}
sum(1, 2, 3, 4); // 10

参数对象可能看起来像一个数组，但它是一个普通的对象，继承自 Object.prototype ，但是如果你想在它上面使用Array方法，你可以直接从 Array.prototype ，例如，获取真实数组的常见模式是使用数组切片方法：

The arguments object may look like an array, but it is a plain object, that inherits from Object.prototype, but if you want to use Array methods on it, you can invoke them directly from the Array.prototype, for example, a common pattern to get a real array is to use the Array slice method:

function test () {
  var args = Array.prototype.slice.call(arguments);
  return args.join(" ");
}
test("hello", "world"); // "hello world"

此外，您可以知道函数期望的参数数量，使用函数对象的 length 属性：

Also, you can know how many arguments a function expects, using the length property of the function object:

function test (one, two, three) {
  // ...
}
test.length; // 3

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