为什么要改变构造函数? [英] Why is the constructor changed?

问题描述

为什么添加原型后构造函数从Foo变成了Object?如何访问原始构造函数?

Why does the constructor change from Foo to Object after adding a prototype? How can I get access to the original constructor?

代码:

function Foo() {}
var foo1 = new Foo();
console.log('foo1: ' + foo1.constructor);

Foo.prototype = {}
var foo2 = new Foo();
console.log('foo2: ' + foo2.constructor);

输出:

foo1: function Foo() {}

foo2: function Object() {
    [native code]
}

http://jsfiddle.net/vDCTJ/

推荐答案

发生这种情况是因为您为 Foo 的原型提供了一个全新的对象，而您没有设置该对象的构造函数"属性.

It happens because you gave Foo a brand new object for its prototype, and you didn't set that object's "constructor" property.

Foo.prototype = { constructor: Foo };

实例化的函数对象为其原型"属性获取一个对象，该对象已经以这种方式初始化.

Instantiated function objects get an object for their "prototype" property that's already initialized that way.

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