JavaScript knowledge finishing (4) Map and Set

JavaScript knowledge finishing (4) Map and Set

table of Contents

JavaScript knowledge finishing (4) Map and Set

1. Map  

1, js creates a map object

2. Put the key-value pair into the map object

3. Get the map value according to the key

4. Delete the map specified object

5. Loop through the map

Two, Set

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1. Map  

Store a collection of key-value pairs, a dictionary

1, js creates a map object

var map = new Map();

2. Put the key-value pair into the map object

map.set("key",value)

map.set("key1",value1)

map.set("key2",value2)

3. Get the map value according to the key

map.get(key)

4. Delete the map specified object

delete map[key]
或
map.delete(key)

5. Loop through the map

map.forEach(function(key){
　　console.log("key",key)  //输出的是map中的value值
})

Two, Set

Store disordered and unique elements.

var m=new Map();

add(value) :向集合添加一个新的值
delete(value) : 删除集合中的一个值
has(value) : 检测一个值是否在集合中 返回 true/false
clear() :清空集合
size() : 返回集合的数量
values() : 返回一个包含所有值的数组