JavaScript继承：当构造函数有参数时 [英] JavaScript inheritance: when constructor has arguments

问题描述

使用纯JavaScript进行继承，这就是我通常所做的事情：

Using pure JavaScript to do inheritance, this is what I usually do:

function A() {}
A.prototype.run = function () {};

function B() {}
B.prototype = new A;
B.prototype.constructor = B;

由于没有参数传递给构造函数，新的A没有什么可抱怨的。现在，如果构造函数有参数传递，我还没有想出一个很好的继承方法。例如，

Since there is no arguments to pass into the constructor, new A has nothing to complain about. Now, I haven't figured out a good way to do inheritance if the constructor has arguments to pass. For example,

function A(x, y) {}
A.prototype.run = function () {};

function B(x, y) {}
B.prototype = new A;
B.prototype.constructor = B;

我可以传递一些任意值，如：

I could pass some arbitrary values like:

B.prototype = new A(null, null);

在某些情况下，我可能需要在A的构造函数中验证x和y。在某些极端在检查x或y时，我需要抛出错误。然后，B无法使用新A从A继承。

In some cases, I may need to validate x and y in the constructor of A. In some extreme cases, I need throw errors when checking x or y. Then, there is no way for B to inherit from A using new A.

有任何建议吗？

谢谢！

推荐答案

好吧，如果你想做 B.prototype 一个继承自 A.prototype 的对象，而不执行 A 构造函数，为避免所有可能的副作用，您可以使用虚拟构造函数来执行此操作，例如：

Well, if you want to make B.prototype an object that inherits from A.prototype, without executing the A constructor, to avoid all possible side-effects, you could use a dummy constructor to do it, for example:

function tmp() {}
tmp.prototype = A.prototype;
B.prototype = new tmp();
B.prototype.constructor = B;

你可以创建一个函数来封装这个新对象的创建逻辑，例如：

You could create a function to encapsulate the logic of the creation of this new object, e.g.:

function inherit(o) {
  function F() {}; // Dummy constructor
  F.prototype = o; 
  return new F(); 
}

//...
B.prototype = inherit(A.prototype);
B.prototype.constructor = B;

如果您定位现代浏览器，则可以使用ECMAScript 5 Object.create 用于相同目的的方法，例如：

If you target modern browsers, you could use the ECMAScript 5 Object.create method for the same purpose, e.g.:

B.prototype = Object.create(A.prototype);
B.prototype.constructor = B;
//..

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