class继承
class People { constructor(name, age) { this.name = name this.age = age } eat() { console.log('I can eat') }}class Student extends People{ constructor(name, age, xuehao) { super(name, age) this.xuehao = xuehao } read() { console.log('I read') }}const xiaoming = new Student('小明', 16, 8888)console.log(xiaoming)xiaoming.eat() // I can eatxiaoming.read() // I read原型链继承
function People(name, age) { if (name) this.name = name if (age) this.age = age}People.prototype.eat = function() { console.log('I can Eat')}function Student(name, age, xuehao) { People.call(this, name, age) this.xuehao = xuehao}/** * 通过将构造函数（Student）的原型（prototype）指向另一个对象（People）的实例， * 这是实现原型链继承的最佳技术计划。 * */ Student.prototype = new People()/** * 然而这样做了之后，Student.prototype.constructor的值就变了，不再是Student了。 * 所以须要通过Object.defineProperty办法将Student.prototype上的constructor再改成Student。 * 其实，当Student.prototype = new People()执行后，Student.prototype是People的一个实例， * Student.prototype自身没有constructor属性，Student.prototype.constructor其实会去原型链下来找，也就是： * Student.prototype.constructor * === Student.prototype.__proto__.constructor * === People.prototype.construcctor === People * (实例的隐式原型__proto__等于其构造函数的显式原型prototype，所以有Student.prototype.__proto__ === People.prototype) * (而构造函数People的显式原型属性prototype上的constructor指向自身，所以有People.prototype.construcctor === People) */Object.defineProperty(Student.prototype, 'constructor', { enumerable: false, value: Student, writable: true})Student.prototype.read2 = function() { console.log('I read')}const xialuo = new Student('着落', 17, 6666)console.log(xialuo)xialuo.eat() // I can eatxialuo.read2() // I read