1. 如何用class实现继承

// 父类
class People{constructor(name){this.name = name}eat(){console.log(`${this.name} eat something`)}
}// 子类
class Student extends People{constructor(name, number){super(name)this.number = number}sayHi(){console.log(`姓名：${this.name}，学号：${this.number}`)}
}class Teacher extends People{constructor(name, major){super(name)this.major = major}teach(){console.log(`${this.name} 教 ${this.major}`)}
}// 实例
const ll = new Student('李雷', 1234)
console.log(ll.name)
console.log(ll.number)
ll.sayHi()
ll.eat()// 实例
const wanglaoshi = new Teacher('王老师', '语文')
console.log(wanglaoshi.name)
console.log(wanglaoshi.major)
wanglaoshi.teach()
wanglaoshi.eat()

效果

2. 类型判断 - instanceof

console.log(ll instanceof Student)    // true
console.log(ll instanceof People)     // true
console.log(ll instanceof Object)     // trueconsole.log([] instanceof Array)   // true
console.log([] instanceof Object)  // trueconsole.log({} instanceof Object)   // true

3. 原型

实例的隐式原型(__proto__)指向构造函数的显示原型(prototype)。

// class 实际上是函数，可见是语法糖
console.log(typeof People)
console.log(typeof Student)// 隐式原型
console.log(ll.__proto__)
// 显示原型
console.log(Student.prototype)console.log(ll.__proto__ === Student.prototype)

获取属性ll.name或执行方法ll.sayHi()、ll.eat()时，现在自身属性和方法中寻找，如ll.name和ll.sayhi()都在自身属性和方法。如果找不到，则自动去__proto__中查找，如ll.eat()。

4. 原型链

// 原型链
console.log(Student.prototype.__proto__)
console.log(People.prototype)
console.log(People.prototype === Student.prototype.__proto__)

5. 手写简易的jQuery

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