ES6's new data container map

map No grammar sugar  

There are only standard creation statements

var map1=new Map([["age",100],[20,"hello"],[a,90]])// initialization 

 

  Something like this is map data

The parameter passed in is an array , There are three data in the array , The first three data are key The back is value

key Can be any type of data It can be said to be basic type data , It can also be reference data

var re1=map1.get("age")
			var re2=map1.get(20)
			var re3=map1.get(["key"])
			var re4=map1.get(a)
			console.log(re1,re2,re3,re4)

Use get Function to get data

！！！ The problem that needs attention is ： We can't be like re3 Take like this , Because this is not the same reference , This is a re created reference , We can only access this data through the same reference

map1.set("life",1)
			map1.set("age",1)
			console.log(map1)
			console.log(map1.size)

  You can see that the new value overrides the old value , If map There is this in the data key Then the new value will overwrite , Add if not

Use set Function to store data

	map1.set("life",1)
			map1.set("age",1)
			console.log(map1)
			console.log(map1.size)
			map1.delete(20)
			var re5=map1.delete("age")
			var re6=map1.delete("age")
			console.log(map1,re5,re6)

 

You can see the use of delete The return value of the function is a Boolean value

map1.clear()
			console.log(map1)

 clear The function is used to empty the array

Take a large example

var mycar = {
				data: new Map(),// data source   The data source passed in from the back end is converted into what we want to use map data 
				clear:function(){// Empty function 
					this.data.clear()
				},
				jianshao:function(id){// Reduction function   The idea is based on count Cannot be less than or equal to 0 Then click one to call the primary function   According to the dishes id Find the data   Reduce count Number 
					let obj=this.data.get(id)
					if(obj){
						obj.count--
						if(obj.count<=0){
							this.data.delete(id)
						}
					}
				},
				add: function(id) {// Add function   Similar to the reduction function, but the first thing we need to judge is whether the dish exists 
					let obj = this.data.get(id)
					if (obj) {
						// console.log(obj)
						obj.count++
						this.data.set(id, obj)
					}
				},
				total: function() {// Total price   Traversal data 
					var result = 0;
					this.data.forEach(function(el) {
						console.log(el)
						result += el.count * el.price
					})
					return result
				},
				network: function() {// Fake data 
					var jiashuju = [{
						id: 435123,
						title: " Yu-Shiang Shredded Pork ",
						price: 18,
						count: 1
					}, {
						id: 435124,
						title: " Dongpo's braised pork ",
						price: 28,
						count: 1
					}, {
						id: 435125,
						title: " Steamed Rice ",
						price: 2,
						count: 2
					}];
					this.data.set(jiashuju[0].id,jiashuju[0])
					this.data.set(jiashuju[1].id,jiashuju[1])
					this.data.set(jiashuju[2].id,jiashuju[2])
					var self = this
					jiashuju.map(function(el) {
						self.data.set(el.id, el)
					})
				}
			}
			mycar.network()
			mycar.add(435123)
			mycar.add(435125)
			mycar.add(435125)
			mycar.add(435125)
			mycar.add(435125)
			mycar.add(435125)
			mycar.jianshao(435124)
			console.log(mycar.data)
			var re1 = mycar.total()
			console.log(re1)
			mycar.clear()
			console.log(mycar.data)