Map function

Let's create a Map function to transform the contents of a Collection.

First, let's define Object to be the empty interface type and create a Collection type to be a slice of objects:

package main
import "fmt"
type Object interface{}
type Collection []Object
func NewCollection(size int) Collection {
     return make(Collection, size)
}

The NewCollection function creates a new instance of the collection with the given size:

type Callback func(current, currentKey, src Object) Object

The Callback type is a first-class function type that returns the calculated result:

func Map(c Collection, cb Callback) Collection {
     if c == nil {
          return Collection{}
     } else if cb == nil {
          return c
     }
     result := NewCollection(len(c))
     for index, val := range c {
          result[index] = cb(val, index, c)
     }
     return result
}

The Map function returns a new collection where every element is the result of calling the Callback function.