2020-09-01- ES6 Map对象使用

逃离我推掉我的手 2022-12-03 05:24 159阅读 0赞

###  1.基本的操作：增删改查 ###

<!DOCTYPE html>
    <html lang="en">
    <head>
    	<meta charset="UTF-8">
    	<meta name="viewport" content="width=device-width, initial-scale=1.0">
    	<title>Document</title>
    </head>
    <body>
    	
    </body>
    </html>
    <script>
    	/* let map=new Map();
    	map.set('name','yangdongxu');
    	map.set('age','30');
    	map.set(function(){},'30');
    	map.set({},'30');
    	console.log(map);
    	console.log(map.size); */
    	//设置值：
      let map=new Map([["name",'怒放的生命'],['height','175']]);
      map.set('goods','apple');
      map.set('bus','q5');
      //判断值是否存在
      let j=map.has('goods');
      console.log(j);//true
      console.log(map.get('goods'));//apple
      //删除某个元素
      map.delete('bus');
      //清除所有元素
      map.clear();
    </script>

### 2.遍历数据 ###

### 3.map类型转换操作 ###

<!DOCTYPE html>
    <html lang="en">
    <head>
    	<meta charset="UTF-8">
    	<meta name="viewport" content="width=device-width, initial-scale=1.0">
    	<title>Document</title>
    </head>
    <body>
    	
    </body>
    </html>
    <script>
    	//转换操作
      let map=new Map([["name",'怒放的生命'],['height','175']]);
      map.set('goods','apple');[["name",'怒放的生命'],['height','175']]
      map.set('bus','q5');
      console.log([...map]);/* (4) [Array(2), Array(2), Array(2), Array(2)]
    0: (2) ["name", "怒放的生命"]
    1: (2) ["height", "175"]
    2: (2) ["goods", "apple"]
    3: (2) ["bus", "q5"] */
      console.log([...map.entries()]);/* (4) [Array(2), Array(2), Array(2), Array(2)]
    0: (2) ["name", "怒放的生命"]
    1: (2) ["height", "175"]
    2: (2) ["goods", "apple"]
    3: (2) ["bus", "q5"] */
    console.log([...map.keys()]);/* ["name", "height", "goods", "bus"] */
    console.log([...map.values()]);/* ["怒放的生命", "175", "apple", "q5"]*/
    for( let [key,val] of map){
       console.log(key,val);
    }
    /* 
    name 怒放的生命
    demo.html:32 height 175
    demo.html:32 goods apple
    demo.html:32 bus q5
     */
     //获取指定值的map数据
     let newArr=[...map].filter((item)=>{
       return item[1].includes('apple')
     })
     console.log(newArr);
     let getData=new Map(newArr);
     console.log([...getData.values()]);//['apple']
    </script>