JavaScript prototype备忘

__proto__：所有对象都有的属性。

var obj = {};
console.log(obj.__proto__); //{}
var obj1 = new Object();
console.log(obj1.__proto__); //{}
var func = function() {};
console.log(func.__proto__); //[Function:Empty]

prototype：函数对象中的属性。

var obj = {};
var func = function() {};
console.log(func.prototype);  //{}
console.log(obj.prototype); //undefined

所有对象的root为object，object的__proto__为null

var obj = {};
console.log(obj.__proto__); //{}
console.log(obj.__proto__.__proto__); //null

var func = function() {};
console.log(func.__proto__); //[Function:Empty]
console.log(func.__proto__.__proto__); //{}
console.log(func.__proto__.__proto__.__proto__);//null

使用构造函数创建的对象中，__proto__为构造函数的prototype指向的对象

var Func = function() {};
Func.prototype.name = ‘f1‘;
console.log(Func.prototype); //{name:‘f1‘}
var obj = new Func();
console.log(obj.__proto__); //{name:‘f1‘}
console.log(Func.prototype==obj.__proto__); //true

实现继承时，__proto__的指向：dog1 instance->Dog.prototype->Animal.prototype->object->null

function Animal() {}
Animal.prototype.name = ‘animal‘;
function Dog() {}
Dog.prototype = new Animal();
Dog.prototype.height = 10;console.log(Animal.prototype); //{name:‘animal‘}console.log(Dog.prototype); //{height:10}

var dog1 = new Dog();
console.log(dog1); //{}
console.log(dog1.__proto__); //{height:10}
console.log(dog1.__proto__.__proto__); //{name:‘animal‘}
console.log(dog1.__proto__.__proto__.__proto__);//{} object
console.log(dog1.__proto__.__proto__.__proto__.__proto__);//null root

console.log(dog1.name); //animalconsole.log(dog1.height); //10

额，，刚学JavaScript，暂时就想到这么多。