text: if (!Array.prototype.myMap) {
    Array.prototype.myMap = function(projectedCb) {
      var results = []
      this.forEach(function(item) {
        results.push(projectedCb(item))
      })
  
      return results
    }
  }
  
  [1, 2, 3, 4, 5].myMap(i => i * 2)
  // => Array(5) [ 2, 4, 6, 8, 10 ]
  