prototype
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/prototype
Object.prototype 属性表示 Object 的原型对象。
prototype.__proto__
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/proto
Object.prototype 的 __proto__ 属性是一个访问器属性（一个getter函数和一个setter函数）, 暴露了通过它访问的对象的内部[[Prototype]] (一个对象或 null)。
prototype.constructor
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor
返回创建实例对象的 Object 构造函数的引用。注意，此属性的值是对函数本身的引用，而不是一个包含函数名称的字符串。对原始类型来说，如1，true和"test"，该值只可读。
<!DOCTYPE html><html lang="zh-CN"><head> ?<meta charset="UTF-8"> ?<title>Document</title></head><body> ?<script> ???// Person ???var Person = function(name) { ?????this.name = name; ?????this.canTalk = true; ???}; ???Person.prototype.greet = function() { ?????if (this.canTalk) { ???????console.log(‘Hi, I am ‘ + this.name); ?????} ???}; ???// Employee ???var Employee = function(name, title) { ?????Person.call(this, name); ?????this.title = title; ???}; ???Employee.prototype = Object.create(Person.prototype); ???Employee.prototype.constructor = Employee; ???Employee.prototype.greet = function() { ?????if (this.canTalk) { ???????console.log(‘Hi, I am ‘ + this.name + ‘, the ‘ + this.title); ?????} ???}; ???// instantiation ???var joe = new Person(‘Joe‘); ???var bob = new Employee(‘Bob‘, ‘Builder‘); ???// call function ???joe.greet(); ???bob.greet(); ???// 直接打印 ???console.log(Person, Employee, joe , bob) ???// prototype：当前对象的原型对象 ???console.log(Person.prototype, Employee.prototype, joe.prototype, bob.prototype) ???// constructor：返回当前对象构造函数的引用 ???console.log(Person.constructor, Employee.constructor, joe.constructor , bob.constructor) ???// __proto__：返回当前对象构造函数的原型 ???console.log(Person.__proto__, Employee.__proto__, joe.__proto__, bob.__proto__) ???console.log(Person.constructor.prototype, Employee.constructor.prototype, joe.constructor.prototype, bob.constructor.prototype) ?</script> ?<script> ?????</script></body></html>JS-prototype
原文地址：https://www.cnblogs.com/jffun-blog/p/9110269.html