JavaScriptSet与Map数据结构详细分析

<script>
    // 声明一个 set
    let s = new Set([1,2,2,3,4,4,5]) //Set方法会自动去重
    // 添加新的元素
    console.log(s.add(6));
</script>

<script>
    // 声明一个 set
    let s = new Set([1,2,2,3,4,4,5]) //Set方法会自动去重
    // 删除元素
    s.delete(1)
    console.log(s);
</script>

<script>
    let arr = [1,2,2,3,4,4,5,6]
    let result = [...new Set(arr)]
    console.log(result);// [1, 2, 3, 4, 5, 6]
</script>

<script>
    // 声明一个 set
    let s = new Set([1,2,2,3,4,4,5]) //Set方法会自动去重
    // 检测
    console.log(s.has(2));//true
</script>

<script>
    // 声明一个 set
    let s = new Set([1,2,2,3,4,4,5]) //Set方法会自动去重
    // 清空
    console.log(s.clear());//undefined
</script>

<script>
    // 声明一个 set
    let s = new Set([1,2,2,3,4,4,5]) //Set方法会自动去重
    // 遍历
    for(let v of s){
        console.log(v);//1,2,3,4,5
    }
</script>

<script>
    let arr = [1,2,3,4,4,5,4,3,1,2,6]
    let arr2 = [3,4,5,1,4,7,8]
    // 先去重，避免重复数字比较降低效率
    let result = [...new Set(arr)].filter(item=>{
        // 对arr2进行去重
        let newarr2 = new Set(arr2)
        if(newarr2.has(item)){
            return true
        }else{
            return false
        }
    })
    // 简写形式
    // let result = [...new Set(arr)].filter(item=>new Set(arr2).has(item)) 
    console.log(result);//[1, 3, 4, 5]
</script>

<script>
    let arr = [1,2,3,4,4,5,4,3,1,2,6]
    let arr2 = [3,4,5,1,4,7,8]
    let uNIOn = [...new Set([...arr,...arr2])]
    console.log(union);
</script>

<script>
    let arr = [1,2,3,4,4,5,4,3,1,2,6]
    let arr2 = [3,4,5,1,4,7,8]
    // 差集是交集的逆运算，主体的不同决定结果的不同
    let diff = [...new Set(arr)].filter(item => !(new Set(arr2).has(item)))
    console.log(diff);//[2, 6]
</script>

<script>
    let set = new Set(['red', 'green', 'blue',1]);
    for (var item of set.keys()) {
        console.log(item);
    }
    for (var item1 of set.values()) {
        console.log(item1);
    }
    console.log(item === item1);//true
</script>

<script>
    let set = new Set(['red', 'green', 'blue',1]);
    for (var item of set.entries()) {
        console.log(item);
    }
</script>

<script>
    let set = new Set(['red', 'green', 'blue',1]);
    set.forEach((value,key)=>console.log(key +':'+value))
</script>

<script>
    // 声明 Map
    let m = new Map()
    // 添加元素
    m.set('world',4)
    m.set('hello',function(){
        console.log('abc');
    })
    let person = {
        name:'张三'
    }
    m.set(person,[5,6,7])
    console.log(m);
</script>

<script>
    // 声明 Map
    let m = new Map()
    let person = function(){
        console.log('hello world');
    }
    m.set(person,'HELLO WPRLD')
    m.set('people',[1,2,3])
    console.log(m);//Map(2)
    // 删除元素
    m.delete('people')
    console.log(m);//Map(1)
</script>

<script>
    // 声明 Map
    let m = new Map()
    // 获取元素
    let person = function(){
        console.log('hello world');
    }
    m.set(person,'HELLO WPRLD')
    console.log(m.get(person))//HELLO WPRLD
</script>

<script>
    // 声明 Map
    let m = new Map()
    m.set('a',1)
    m.set(2,'b')
    m.set('c',3)
    // 检测键名是否存在
    console.log(m.has(1));//false
    console.log(m.has(2));//true
</script>

<script>
    // 声明 Map
    let m = new Map()
    m.set('a',1)
    m.set(2,'b')
    m.set('c',3)
    // 清除所有
    m.clear()
    console.log(m);//Map(0)
</script>