Javascript`new`运算符&原型 [英] Javascript `new` operator & prototype

问题描述

假设我们创建一个名为'Shape'的函数，并添加一个属性'name'&方法'toString'在它的原型：

Say we create a Function named 'Shape', and add a property 'name' & method 'toString' on it's prototype:

var Shape = function () {};
Shape.prototype.name = 'Shape';
Shape.prototype.toString = function () {
    return this.name;
}

console.log(Shape.name); // ''
console.log(Shape.toString()); // function () {}

var Triangle = new Shape();
console.log(Triangle.name); // 'Shape'
console.log(Triangle.toString()); // 'Shape'

'NEW'操作符做了两件事：
这个到'Triangle'
2.它将三角形的[[proto]]指向Shape.prototype

'NEW' operator did two things: 1. It points this to 'Triangle' 2. It points 'Triangle's [[proto]] to Shape.prototype

然后我可以理解当我调用name& toString on Triangle，它搜索它的原型链，直到Shape.prototype。

Then I can understand when I call name & toString on Triangle, it searches for it's prototype chain till Shape.prototype.

但是我的问题是为什么不是Shape搜索它的属性&属性？

But my problem is why not Shape searching for it's property(even it's an Object) for the method & property?

感谢。

推荐答案

我知道。

这里 Shape 是一个函数&一个函数只是一种特殊类型的对象，和任何对象一样，一个函数可以有属性。

Here Shape is a function & A function is just a special kind of object, and like any object a function can have properties.

函数自动获得一个名为 code>，这只是一个空对象。

Functions automatically get a property called prototype, which is just an empty object. This object gets some special treatment.

当你做新 c> Function 所创建的对象将继承其构造函数原型的所有属性。

When you will do a new of a Function the created object inherits all of the properties of its constructor’s prototype.

喜欢下面

var Shape = function () {};
Shape.prototype.name = 'Shape';
Shape.prototype.toString = function () {
    return this.name;  
}

当你说

var Triangle = new Shape();

所以它做什么

var Triangle = {};
Triangle.name = Shape.prototype.name
Triangle.toString = Shape.prototype.toString;

它设置对象 Triangle to delegate to Shape.prototype。

"it sets up the object Triangle to delegate to Shape.prototype."

所以当你做

Triangle.name //Shape
Triangle.toString() // Shape

但是 Shape 你必须说

Shape.prototype.name //Shape
Shape.prototype.toString() //Shape

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