js中一些api的实现

Array.prototype.myReverse = function () {
  if (this instanceof Array) {
    //如果是数组
    let len = this.length,
      i = this.length - 1;
    let res = []; //定义一个数组
    for (i; i >= 0; i--) {
      res.push(this[i]);
    }
    this.length = 0; //清空原数组
    Array.prototype.splice.apply(this, [0, 0, res]); //将新结果插入到原数组中
  } else {
    //处理类数组
    let keys = [],
      values = [];
    let len = this.length;
    delete this["length"];

    for (let k in this) {
      keys.push(k);
      values.push(this[k]);
    }
    for (let i = 0, l = keys.length; i