现在不需要加糖的函数'类'或使用'New'。使用对象字面量。

Object原型已经是一个“类”。当你定义一个对象文字时，它已经是原型对象的一个实例。这些也可以作为另一个对象的原型，等等。

const Person = {
  name: '[Person.name]',
  greeting: function() {
    console.log( `My name is ${ this.name || '[Name not assigned]' }` );
  }
};
// Person.greeting = function() {...} // or define outside the obj if you must

// Object.create version
const john = Object.create( Person );
john.name = 'John';
console.log( john.name ); // John
john.greeting(); // My name is John 
// Define new greeting method
john.greeting = function() {
    console.log( `Hi, my name is ${ this.name }` )
};
john.greeting(); // Hi, my name is John

// Object.assign version
const jane = Object.assign( Person, { name: 'Jane' } );
console.log( jane.name ); // Jane
// Original greeting
jane.greeting(); // My name is Jane 

// Original Person obj is unaffected
console.log( Person.name ); // [Person.name]
console.log( Person.greeting() ); // My name is [Person.name]

这里值得一读:

Class-based object-oriented languages, such as Java and C++, are founded on the concept of two distinct entities: classes and instances. ... A prototype-based language, such as JavaScript, does not make this distinction: it simply has objects. A prototype-based language has the notion of a prototypical object, an object used as a template from which to get the initial properties for a new object. Any object can specify its own properties, either when you create it or at run time. In addition, any object can be associated as the prototype for another object, allowing the second object to share the first object's properties

编辑，其实我错了。注释掉一行并不会改变它的行为。(我测试过)

是的，这是必要的。当你这样做时

Student.prototype = new Person();  

student。prototype。constructor变成Person。因此，调用Student()将返回Person创建的对象。如果你这样做了

Student.prototype.constructor = Student; 

Student.prototype.constructor被重置回Student。现在，当您调用Student()时，它执行Student，它调用父构造函数parent()，它返回正确继承的对象。如果你在调用Student.prototype.constructor之前没有重置它，你将得到一个没有在Student()中设置的任何属性的对象。

给定简单构造函数:

function Person(){
    this.name = 'test';
}


console.log(Person.prototype.constructor) // function Person(){...}

Person.prototype = { //constructor in this case is Object
    sayName: function(){
        return this.name;
    }
}

var person = new Person();
console.log(person instanceof Person); //true
console.log(person.sayName()); //test
console.log(Person.prototype.constructor) // function Object(){...}

默认情况下(来自规范https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor)，所有原型都会自动获得一个称为constructor的属性，该属性指向属性所在的函数。 根据构造函数的不同，可能会将其他属性和方法添加到原型中，这不是很常见的做法，但仍然允许进行扩展。

所以简单地回答:我们需要确保原型中的值。构造函数被正确地设置为规范所假定的样子。

我们必须总是正确地设置这个值吗?它有助于调试，并使内部结构与规范保持一致。当我们的API被第三方使用时，我们肯定应该这样做，但当代码最终在运行时执行时，我们不应该这样做。

当你需要toString的替代而不需要monkeypatching时，它是必要的:

//Local foo = []; foo.toUpperCase = String(foo).toUpperCase; foo.push("a"); foo.toUpperCase(); //Global foo = []; window.toUpperCase = function (obj) {return String(obj).toUpperCase();} foo.push("a"); toUpperCase(foo); //Prototype foo = []; Array.prototype.toUpperCase = String.prototype.toUpperCase; foo.push("a"); foo.toUpperCase(); //toString alternative via Prototype constructor foo = []; Array.prototype.constructor = String.prototype.toUpperCase; foo.push("a,b"); foo.constructor(); //toString override var foo = []; foo.push("a"); var bar = String(foo); foo.toString = function() { return bar.toUpperCase(); } foo.toString(); //Object prototype as a function Math.prototype = function(char){return Math.prototype[char]}; Math.prototype.constructor = function() { var i = 0, unicode = {}, zero_padding = "0000", max = 9999; while (i < max) { Math.prototype[String.fromCharCode(parseInt(i, 16))] = ("u" + zero_padding + i).substr(-4); i = i + 1; } } Math.prototype.constructor(); console.log(Math.prototype("a") ); console.log(Math.prototype["a"] ); console.log(Math.prototype("a") === Math.prototype["a"]);

我不同意。不需要设置原型。取完全相同的代码，但去掉原型。构造函数。有什么变化吗?不。现在，进行以下更改:

Person = function () {
    this.favoriteColor = 'black';
}

Student = function () {
    Person.call(this);
    this.favoriteColor = 'blue';
}

在测试代码的末尾……

alert(student1.favoriteColor);

颜色是蓝色的。

对原型的更改。构造函数，根据我的经验，没有做太多，除非你做非常具体，非常复杂的事情，这可能不是一个好的实践:)

Edit: After poking around the web for a bit and doing some experimentation, it looks like people set the constructor so that it 'looks' like the thing that is being constructed with 'new'. I guess I would argue that the problem with this is that javascript is a prototype language - there is no such thing as inheritence. But most programmers come from a background of programming that pushes inheritence as 'the way'. So we come up with all sorts of things to try and make this prototypical language a 'classic' language.. such as extending 'classes'. Really, in the example they gave, a new student is a person - it isn't 'extending' from another student.. the student is all about the person, and whatever the person is the student is as well. Extend the student, and whatever you've extended is a student at heart, but is customized to fit your needs.

克罗克福德有点疯狂和过分热心，但认真阅读他写的一些东西。它会让你从不同的角度看待这个问题。

这有一个巨大的陷阱，如果你写

Student.prototype.constructor = Student;

但如果有一个老师，他的原型也是人，你写

Teacher.prototype.constructor = Teacher;

那么学生构造函数现在是老师!

编辑: 您可以通过确保您已经使用使用Object创建的Person类的新实例设置了Student和Teacher原型来避免这种情况。创建，如Mozilla示例中所示。

Student.prototype = Object.create(Person.prototype);
Teacher.prototype = Object.create(Person.prototype);