实现一个filter方法

    // 实现一个filter方法
    let x = [2, 3, 1, 3, 5]
    Array.prototype._filter = function (fn) {
      if (typeof fn !== "function") {
        throw new TypeError('Not Function')
      }
      let res = []
      for (let i of this) {
        if (fn(i)) res.push(i)
      }
      return res
    }
    console.log(x._filter(x => x > 2)); // 3,3,5