面型对象和UML类图

面向对象

why?

1.程序执行：顺序，判断，循环，----结构化

2.面向对象----数据结构化

3.面向计算机，结构化的才是最简单的

4.变成应该简单&抽象

一个基本的类

class People {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  eat() {
    alert(`${this.name} eat something`);
  }
  speak() {
    alert(`My name is ${this.name}, age ${this.age}`);
  }
}

let zhang = new People("zhang", 20);
zhang.eat();
zhang.speak();

let wang = new People("wang", 21);
wang.eat();
wang.speak();

继承

class People {
  constructor(name, age) {
    this.name = name;
    this.age = age;
  }
  eat() {
    alert(`${this.name} eat something`);
  }
  speak() {
    alert(`My name is ${this.name}, age ${this.age}`);
  }
}

class Student extends People {
  constructor(name, age, number) {
    super(name, age);
    this.number = number;
  }
  study() {
    alert(`${this.name} study`);
  }
}

let xiaoming = new Student("xiaoming", 10, "A1");
xiaoming.study();
console.log(xiaoming.number);
let xiaohong = new Student("xiaohong", 11, "A2");
xiaohong.study();

多态

同一个接口，不同表现
js 应用极少
需要结合 java 等语言的接口，重写，重载等功能
保持子类的开放性和灵活性
面向接口编程
（js 引用极少）

class People {
  constructor(name) {
    this.name = name;
  }
  saySomething() {}
}
class A extends People {
  constructor(name) {
    super(name);
  }
  saySomething() {
    alert("I am A");
  }
}
class B extends People {
  constructor(name) {
    super(name);
  }
  saySomething() {
    alert("I am B");
  }
}
let a = new A("a");
a.saySomething();
let b = new B("b");
b.saySomething();

封装

减少耦合，不该外露的不外露
利于数据，接口的管理
es6 不支持，一般认为，_开头的属性是 private

封装在 es6 中无法体现，因为是通过 public，protect，和 private 体现的，但在 ts 中可以体现

class People {
  // ts中严格：变量要使用先定义，默认为public
  name;
  age;
  protected weight; //受保护的属性只有自己可访问
  constructor(name, age) {
    this.name = name;
    this.age = age;
    this.weight = 120;
  }
  eat() {
    alert(`${this.name} eat something`);
  }
  speak() {
    alert(`My name is ${this.name}, age ${this.age}`);
  }
}

class Student extends People {
  number;
  private girlfriend;
  constructor(name, age, number) {
    super(name, age);
    this.number = number;
    this.girlfriend = "ygj";
  }
  study() {
    alert(`${this.name} study`);
  }
  getweight() {
    alert(`${this.weight}`);
  }
}

let xiaoming = new Student("zhang", 20, "11");
xiaoming.getweight(); //不报错
alert(xiaoming.girlfriend); //报错
alert(xiaoming.weight); //报错

let wang = new People("wang", 21);
wang.eat();
wang.speak();

jQuery 使用类的示例

class jQuery {
  constructor(selector) {
    let slice = Array.prototype.slice;
    let dom = slice.call(document.querySelectorAll(selector));
    let len = dom ? dom.length : 0;
    for (let i = 0; i < len; i++) {
      this[i] = dom[i];
    }
    this.length = len;
    this.selector = selector || "";
  }
  append(node) {}
  addClass(name) {}
  html(data) {}
  // 此处省略若干 API
}
window.$ = function(selector) {
  return new jQuery(selector);
};

// 测试代码

var $p = $("p");
console.log($p);
console.log($.addClass);