面试热点: 你能模拟实现 new 操作符吗

// 现实中瘦不了，但网络中一定要保持苗条
function Thin_User(name, age) {
    this.name = name;
    this.age = age;
}
Thin_User.prototype.eatToMuch = function () {
    // 白日做梦吧
    console.log('i eat so much, but i\'m very thin!!!');
}
Thin_User.prototype.isThin = true;
const xiaobao = new Thin_User('zcxiaobao', 18);
console.log(xiaobao.name);   // zcxiaobao
console.log(xiaobao.age);    // 18
console.log(xiaobao.isThin); // true
// i eat so much, but i'm very thin!!!
xiaobao.eatToMuch(); 
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function Thin_User(name, age) {}
const u1 = new Thin_user(...)
const u2 = createObject(Thin_User, ...a)
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function createObject(Con) {
    // 创建新对象obj
    // var obj = {};也可以
    var obj = Object.create(null);
    // 将obj.__proto__ -> 构造函数原型
    // (不推荐)obj.__proto__ = Con.prototype
    Object.setPrototypeOf(obj, Con.prototype);
    // 执行构造函数
    Con.apply(obj, [].slice.call(arguments, 1));
    // 返回新对象
    return obj;
}
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function Thin_User(name, age) {
    this.name = name;
    this.age = age;
    return 'i will keep thin forever';
}
Thin_User.prototype.eatToMuch = function () {
    console.log('i eat so much, but i\'m very thin!!!');
}
Thin_User.prototype.isThin = true;
const xiaobao = new Thin_User('zcxiaobao', 18);
console.log(xiaobao.name);   // zcxiaobao
console.log(xiaobao.age);    // 18
console.log(xiaobao.isThin); // true
// i eat so much, but i'm very thin!!!
xiaobao.eatToMuch(); 
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function Thin_User(name, age) {
    this.name = name;
    this.age = age;
    return {
        name: name,
        age: age * 10,
        fat: true
    }
}
Thin_User.prototype.eatToMuch = function () {
    // 白日做梦吧，留下肥胖的泪水
    console.log('i eat so much, but i\'m very thin!!!');
}
Thin_User.prototype.isThin = true;
const xiaobao = new Thin_User('zcxiaobao', 18);
// Error: xiaobao.eatToMuch is not a function
xiaobao.eatToMuch();
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function createObject(Con) {
    // 创建新对象obj
    // var obj = {};也可以
    var obj = Object.create(null);
    // 将obj.__proto__ -> 构造函数原型
    // (不推荐)obj.__proto__ = Con.prototype
    Object.setPrototypeOf(obj, Con.prototype);
    // 执行构造函数，并接受构造函数返回值
    const ret = Con.apply(obj, [].slice.call(arguments, 1));
    // 若构造函数返回值为对象，直接返回该对象
    // 否则返回obj
    return typeof(ret) === 'object' ? ret: obj;
}
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