SOURCE

class Animal {
    constructor(name) {
        this.name = name;
    }
}
class Cat extends Animal {
    constructor(name) {
        super(name)
        this.name = name
    }
    say() {
        return 'Hello,' + this.name + '!'
    }
}


// 测试:
var kitty = new Cat('Kitty');
var doraemon = new Cat('哆啦A梦');
if ((new Cat('x') instanceof Animal)
    && kitty
    && kitty.name === 'Kitty'
    && kitty.say
    && typeof kitty.say === 'function'
    && kitty.say() === 'Hello, Kitty!'
    && kitty.say === doraemon.say) {
    console.log('测试通过!');
} else {
    console.log('测试失败!');
}