How to Format a Currency with Commas in Golang

Formatting float to currency string in Go
Created
Modified

Using localized formatting

Use golang.org/x/text/message to print using localized formatting for any language in the Unicode CLDR.

Make a main.go file containing the following:

package main

import (
  "golang.org/x/text/language"
  "golang.org/x/text/message"
)

func main() {

  p := message.NewPrinter(language.English)
  p.Printf("%v\n", 1000)
  p.Printf("%v\n", 1000.02)

}
$ go run main.go
1,000
1,000.02

A classic example of recursion

The argument to comma is a string. If its length is less than or equal to 3, no comma is neces- sary. Otherwise, comma calls itself recursively with a substring consisting of all but the last three characters, and appends a comma and the last three characters to the result of the recur- sive call.

package main

import (
  "fmt"
  "strings"
)

func main() {

  fmt.Println(comma("-100"))
  fmt.Println(comma("1000"))
  fmt.Println(comma("1000.02"))
  fmt.Println(comma(".020"))

}

// comma inserts commas in a non-negative decimal integer string.
func comma(s string) string {

  neg := ""
  if s[0:1] == "-" {
    neg = "-"
    s = s[1:]
  }
  end := strings.Index(s, ".")
  point := ""
  if end >= 0 {
    point = s[end:]
    s = s[0:end]
  }

  n := len(s)
  if n <= 3 {
    return neg + s + point
  }

  return neg + comma(s[:n-3]) + "," + s[n-3:] + point
}
$ go run main.go
-100
1,000
1,000.02
.020

Related Tags

#format# #currency# #comma#

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