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);

uml类图

统一建模语言
类图，uml包含很多种图
关系，泛型，和关联
泛型是指继承（空心）
关联是指引用（实心）