Javascript 手写map 、filter

   // map
      Array.prototype.myMap = function (fn, context) {
        let arr = this, res= []
        for (let i = 0; i < arr.length; i++) {
          res.push(fn.call(context, arr[i], i, arr))
        }
        return res
      }
      // filter
      Array.prototype.myFilter = function (fn, context) {
        let arr = this, res = []
        for (let i = 0; i < arr.length; i++) {
          let result = fn.call(context, arr[i], i, arr)
          result && res.push(arr[i])
        }
        return res
      }