array iteration

Examples of iterating, mapping, filtering, and reducing arrays.

Node.js

  1. const array = ['a', 'b', 'c']
  3. array.forEach((value, i) => {
  4.   console.log(i, value)
  5. })
  7. const mapped = array.map(value => {
  8.   return value.toUpperCase()
  9. })
  11. console.log(mapped)
  13. const filtered = array.filter((value, i) => {
  14.   return i % 2 == 0
  15. })
  17. console.log(filtered)
  19. const reduced = array.reduce((acc, value, i) => {
  20.   if (i % 2 == 0) {
  21.     acc.push(value.toUpperCase())
  22.   }
  24.   return acc
  25. }, [])
  27. console.log(reduced)

Output

  1. 0 'a'
  2. 1 'b'
  3. 2 'c'
  4. [ 'A', 'B', 'C' ]
  5. [ 'a', 'c' ]
  6. [ 'A', 'C' ]

Go

  1. package main
  3. import (
  4.     "fmt"
  5.     "strings"
  6. )
  8. func main() {
  9.     array := []string{"a", "b", "c"}
  11.     for i, value := range array {
  12.         fmt.Println(i, value)
  13.     }
  15.     mapped := make([]string, len(array))
  16.     for i, value := range array {
  17.         mapped[i] = strings.ToUpper(value)
  18.     }
  20.     fmt.Println(mapped)
  22.     var filtered []string
  23.     for i, value := range array {
  24.         if i%2 == 0 {
  25.             filtered = append(filtered, value)
  26.         }
  27.     }
  29.     fmt.Println(filtered)
  31.     var reduced []string
  32.     for i, value := range array {
  33.         if i%2 == 0 {
  34.             reduced = append(reduced, strings.ToUpper(value))
  35.         }
  36.     }
  38.     fmt.Println(reduced)
  39. }

Output

  1. 0 a
  2. 1 b
  3. 2 c
  4. [A B C]
  5. [a c]
  6. [A C]