Question

我试图通过JavaScript传递一个利用继承的测试套件。下面是我到目前为止的代码片段：

var Infant = function() {
    this.age  = 0;
    this.color = 'pink';
    this.food = 'milk';

};
Infant.prototype.eat = function(){
    return this.eat;
}


var Adolescent = function() {

    this.age = 5;
    this.height = 'short';
    this.job = 'keep on growing';

};

我想继承婴儿班的食物和吃法，但我的尝试不足。我最初的想法是分配这个.Adolescent = Infant.food;但那并没有奏效。我知道我需要将婴儿设置为超级课程，但我要旋转我的轮子

Answer 1

在JavaScript中使用构造函数进行继承时，您：

制作＆＃34;派生＆＃34;的prototype属性构造函数一个对象，其原型是＆＃34; base＆＃34;的prototype属性。构造
在＆＃34;派生＆＃34;上设置constructor属性构造函数的prototype属性指向＆＃34;派生的＆＃34;构造
拨打＆＃34; base＆＃34;构造函数来自＆＃34;派生＆＃34;具有正确this。

像这样：

var Infant = function() {
    this.age  = 0;
    this.color = 'pink';
    this.food = 'milk';
};
Infant.prototype.eat = function(){
    return /*...something...*/; // Returning `this.eat` doesn't make any sense, that's the function we're in
};

var Adolescent = function() {

    // #3 Give super a chance to initialize the instance, you can pass args if appropriate
    Infant.call(this);

    this.age = 5;
    this.height = 'short';
    this.job = 'keep on growing';
};

// Set up Adolescent's prototype, which uses Infant's prototype property as its prototype
Adolescent.prototype = Object.create(Infant.prototype); // #1
Adolescent.prototype.constructor = Adolescent;          // #2

Object.create，因此它不会出现在IE8中过时的JavaScript引擎上。上面使用的单参数版本可以是easily shimmed。

在ES2015中，我们可以选择使用新的class语义：

class Infant {
    constructor() {
        this.age  = 0;
        this.color = 'pink';
        this.food = 'milk';
    }

    eat() {
        return /*...something...*/;
    }
}

class Adolescent extends Infant {            // extends does #1 and #2
    constructor() {
        super();                             // #3, you can pass args here if appropriate

        this.age = 5;
        this.height = 'short';
        this.job = 'keep on growing';
    }
}

通过伪经典实例化（JavaScript）抓取原型继承

1 个答案: