考点： URLSearchParams、map、生成器函数

    1. class MyURLSearchParams {
    2.   //  map;
    3.    /**
    4.     * @params {string} init
    5.     */
    6.    constructor(init) {
    7.      this.map = new Map();
    8.      let arr = init.replace(/^\?/, '').split(/\&/);
    9.      for (let item of arr) {
    10.        let [k, v] = item.split('=');
    11.        if (this.map.has(k)) {
    12.          this.append(k, v);
    13.        } else {
    14.          this.set(k, v);
    15.        }
    16.     }
    17.    }
    19.    /** 
    20.     * @params {string} name
    21.     * @params {any} value
    22.     */
    23.    append(name, value) {
    24.      this.map.get(name).push(String(value));
    25.    }
    27.    /**
    28.     * @params {string} name
    29.     */
    30.    delete(name) {
    31.     this.map.delete(name);
    32.    }
    34.    /**
    35.     * @returns {Iterator} 
    36.     */
    37.    * entries() {
    38.      for (let [k, values] of this.map) {
    39.        for (let val of values) {
    40.          yield [k, val]
    41.        }
    42.      }
    43.    }
    45.    /**
    46.     * @param {(value, key) => void} callback
    47.     */
    48.    forEach(callback) {
    49.      for (let [k, values] of this.map) {
    50.        for (let val of values) {
    51.          callback(val, k)
    52.        }
    53.      }
    54.    }
    56.    /**
    57.     * @param {string} name
    58.     * returns the first value of the name
    59.     */
    60.    get(name) {
    61.      return this.map.has(name) ? this.map.get(name)[0] : null;
    62.    }
    64.    /**
    65.     * @param {string} name
    66.     * @return {string[]}
    67.     * returns the value list of the name
    68.     */
    69.    getAll(name) {
    70.      return this.map.has(name) ? this.map.get(name): [];
    71.    }
    73.    /**
    74.     * @params {string} name
    75.     * @return {boolean}
    76.     */
    77.    has(name) {
    78.       return this.map.has(name);
    79.    }
    81.    /**
    82.     * @return {Iterator}
    83.     */
    84.    keys() {
    85.      return this.map.keys();
    86.    }
    88.    /**
    89.     * @param {string} name
    90.     * @param {any} value
    91.     */
    92.    set(name, value) {
    93.      this.map.set(name, [String(value)])
    94.    }
    96.    // sor all key/value pairs based on the keys
    97.    sort() {
    98.      this.map = new Map([...this.map].sort());
    99.    }
    101.    /**
    102.     * @return {string}
    103.     */
    104.    toString() {
    105.      let ans = [];
    106.      for (let [k, values] of this.map) {
    107.        for (let val of values) {
    108.          ans.push(`${k}=${val}`);
    109.        }
    110.      }
    111.      return ans.join('&');
    112.    }
    114.    /**
    115.     * @return {Iterator} values
    116.     */
    117.    * values() {
    118.      for (let [k, values] of this.map) {
    119.        for (let val of values) {
    120.          yield val
    121.        }
    122.      }
    123.    }
    124.  }