如何在 JavaScript 中创建无法实例化的抽象基类 [英] How to create Abstract base class in JavaScript that can't be Instantiated

问题描述

我有一堂课

function Node() {
    //implementation
}

和另一个班级

function AttributionalNode() {
    this.prototype.setAttr = function (attr) {
        this.atText = attr;
    };
}

AttributionalNode.prototype = new Node();
AttributionalNode.prototype.constructor = AttributionalNode;

如何使类 Node() 无法实例化?例如，当我尝试

How to make class Node() so it can't be instantiated? e.g when I try

var node = new Node();

所以它抛出异常?

推荐答案

这行得通:

function Node() {
    if (this.constructor === Node) {
        throw new Error("Cannot instantiate this class");
    }
}

function AttributionalNode() {
    Node.call(this); // call super
}

AttributionalNode.prototype = Object.create(Node.prototype);
AttributionalNode.prototype.setAttr = function (attr) {
    this.atText = attr;
};
AttributionalNode.prototype.constructor = AttributionalNode;

var attrNode = new AttributionalNode();
console.log(attrNode);
new Node();

注意:不能在构造函数内部引用this.prototype，因为原型只是构造函数的一个属性，而不是实例的一个属性.

Note: you cannot refer to this.prototype inside the constructor, as the prototype is only a property of the constructor function, not of the instances.

此外，参见此处关于如何正确扩展 JS 类的好文章.

Also, see here for a good article on how to properly extend JS classes.

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