Map structure

One 、map Object creation

var x=new Map();

var map1 = new Map([
                ['a', 1],
                ['b', 2],
                ['c', 1]
            ]);

Two 、 increase / add to

x.set(Symbol('a'),' Zhang San ');

x.set(Symbol('a'),' Li Si ');

x.set(' zhengzhou ',' a sunny day ');

x.set(' kaifeng ',' cloudy ');

3、 ... and 、 modify

x.set(' kaifeng ',' a sunny day ');

Four 、 lookup

console.log(x.has(' luoyang ')); return true or false

5、 ... and 、 Delete

 x.delete(' kaifeng ');

x.clear(); Empty

6、 ... and 、 Traverse

 

x.forEach(function(val,key,map){
	console.log(val,key)
})

7、 ... and 、 keys /values /entries

	            for(let i of x.keys()){
					console.log(i);
				}
				for(let i of x.values()){
					console.log(i);
				}
				for(let i of x.entries()){
					console.log(i);
				}
				for(let i of x){
					console.log(i);
				}

8、 ... and 、 map transformation key Relationship with value

            var map1 = new Map([
				['a', 1],
				['b', 2],
				['c', 1]
			]);
			var map2 = new Map([
				[' zhengzhou ', ' a sunny day '],
				[' kaifeng ', ' cloudy '],
				[' Tokyo ', ' tsunami '],
				[' xinxiang ', ' tsunami ']
			]);

			function mapchenge(map) {
				console.log(map);
				let tem_map=new Map();// empty map aggregate 
				for(let i of new Set(map.values())){// Iteration after de duplication 
					tem_map.set(i,[]);// Add data to  map aggregate 
				}
				// Add source value   To   new map
				for(let [i,j] of map){
					tem_map.get(j).push(i);
				}
				return tem_map;
			}
			var y = mapchenge(map1);
			var x = mapchenge(map2);
			console.log(y);
			console.log(x);