模拟实现ES6中新存储数据方式Map

Map特点

1.有属性名、属性值，键值对不重复，若属性相同会被新添加的键值对覆盖

2.属性名数据类型：function、{}、NaN、number、[]、undefined、null、boolean、string

3.原型方法：set()、get()、delete()、clear()、has()

模拟实现

hash算法：利用hash算法将属性值转化为0-8之间的，进而放入桶中

桶：利用数组模拟实现桶存储结构

链表：hash算法转化到特定区间的数据，相同的存储到同一链表上

        function Map() {
            this.bucketLength = 8;
            this.init();
        }
        Map.prototype.init = function () {
            this.bucket = new Array (this.bucketLength);
            for (let i = 0; i < this.bucket.length; i ++){
                this.bucket[i] = {
                    type:'bucket' + i,
                    next:null,
                }
            }
        }
        Map.prototype.hash = function (key) {
            let hash = 0;
            if ( typeof key !== 'string'){
                if(typeof key == 'number'){
                    // number NaN    
                    hash = Object.is(key , NaN) ? 0 : key;
                    hash %= 8;
                }else if(typeof key == 'object'){
                    //null {} []
                    hash = 1;
                }else if(typeof key == 'boolean'){
                    //boolean
                    hash = Number(key);
                }else{
                    //undefined function
                    hash = 2;
                }
            }else{
                //string  转化规则：字符串前三位assic码相加求余
                for (let i = 0; i < 3; i++){
                    hash += key[i] ? key[i].charCodeAt(0) : 0;
                }
                hash %= 8;
            }
            return hash;
        }
        Map.prototype.set = function (key,value) {
            let hash = this.hash(key);
            let tempBucket = this.bucket[hash];
            while(tempBucket.next){//！= null
                if(tempBucket.next.key == key){
                    tempBucket.next.value = value;
                    return false;
                }else{
                    tempBucket = tempBucket.next;
                }
            }
            tempBucket.next = {
                key:key,
                value:value,
                next:null
            }
            return true;
        }
        Map.prototype.get = function (key){
            let hash = this.hash(key);
            let tempBucket = this.bucket[hash];
            while(tempBucket){
                if(tempBucket.key == key){
                    return tempBucket.value;
                }else{
                    tempBucket = tempBucket.next;
                }
            }
            return undefined;
        }
        Map.prototype.delete = function (key) {
            let hash = this.hash(key);
            let tempBucket = this.bucket[hash];
            while(tempBucket.next){
                if(tempBucket.next.key == key){
                    tempBucket.next = tempBucket.next.next;
                    return true;
                }else{
                    tempBucket = tempBucket.next;
                }
            }
            return false;
        }
        Map.prototype.has = function (key) {
            let hash = this.hash(key);
            let tempBucket = this.bucket[hash];
            while (tempBucket){
                if(tempBucket.key && tempBucket.key == key){
                    return true;
                }else{
                    tempBucket = tempBucket.next;
                }
            }
            return false;
        }
        Map.prototype.clear = function () {
            this.init();
        }
        let oMap = new Map();
        oMap.set('name','19');
        oMap.get('name');//19