ES6 Map字典实现

class FakeMap {
    constructor(arr=[]) {
        this.items = {};
        this.size = 0;
        arr.forEach(item => {
            this.set(item[0], item[1]);
        });
    }
    has(val) {
        return this.items.hasOwnProperty(val);
    }
    set(key, val) {
        if (this.has(key)) {
            this.items[key] = val;
        } else {
            this.items[key] = val;
            this.size++;
        }
    }
    get(key) {
        return this.has(key)? this.items[key] : undefined;
    }
    delete(key) {
        if (this.has(key)) {
            Reflect.deleteProperty(this.items, key);
            this.size--;
            return true;
        } else {
            return false;
        }
    }
    clear() {
        this.items = {};
        this.size = 0;
    }
    keys() {
        return Object.keys(this.items);
    }
    values() {
        return Object.values(this.items);
    }
    forEach(fn, context) {
        for (let i = 0; i<this.size; i++) {
            let key = this.keys()[i];
            let value = this.values()[i];
            Reflect.apply(fn, context, [key, value]);
        }
    }
}

let map = new FakeMap([[1, 22], ['3', 44]]);
map.set(true, 'boolean');
map.forEach((key, val) => {
    console.log(`${key} : ${val}`);
})
console.log(map)