Es6-- set

Set

characteristic ：

（1） duplicate removal , Added add  Delete delete  testing  has()  situation  clear  Traverse for (let item of set)

Case study 1： Raw data   duplicate removal 、 intersection 、 Combine 、 Difference set

			//  duplicate removal 
            let arr = [1, 2, 3, 3, 3, 4, 4, 5, 6]
            let unique = new Set(arr)

			//  intersection 
            let arr2 = [4, 5, 6, 5, 6]
            let intersection = [...new Set(arr)].filter(item => {
                if (new Set(arr2).has(item)) {
                    return true
                } else {
                    return false
                }
            });
            //  Combine 
            let union = new Set([...arr, ...arr2])
            //  Difference set 
            let diff = [...new Set(arr2)].filter(item => !new Set(arr).has(item))

Case study 2： De duplication of object data

            let arr = [
                {id: 1, name: ' Zhou Yu '},
                {id: 3, name: ' Wang Zhaojun '},
                {id: 2, name: ' Arthur '},
                {id: 1, name: ' Little Joe '},
                {id: 2, name: ' Bridge '},
                {id: 3, name: ' Han xin '}
            ];
            let obj = {}
            arr = arr.reduce((preVal,curVal) => {
                obj[curVal.id] ? "" : obj[curVal.id] = preVal.push(curVal)
                return preVal
            },[])
            console.log(arr)

Map

characteristic

（1）Map Object has key value pairs , The key can be any data type .

（2）Map Object remembers the original insertion order of keys .

（3）Map Object has an attribute that represents the size of the mapping