Strip all whitespace from a string

Here is some benchmarks on a few different methods for stripping all whitespace characters from a string: (source data):

BenchmarkSpaceMap-8                     2000       1100084 ns/op      221187 B/op          2 allocs/op
BenchmarkSpaceFieldsJoin-8              1000       2235073 ns/op     2299520 B/op         20 allocs/op
BenchmarkSpaceStringsBuilder-8          2000        932298 ns/op      122880 B/op          1 allocs/op

• SpaceMap: uses strings.Map; gradually increases the amount of allocated space as more non-whitespace characters are encountered
• SpaceFieldsJoin: strings.Fields and strings.Join; generates a lot of intermediate data
• SpaceStringsBuilder uses strings.Builder; performs a single allocation, but may grossly overallocate if the source string is mainly whitespace.

package main_test

import (
    "strings"
    "unicode"
    "testing"
)

func SpaceMap(str string) string {
    return strings.Map(func(r rune) rune {
        if unicode.IsSpace(r) {
            return -1
        }
        return r
    }, str)
}

func SpaceFieldsJoin(str string) string {
    return strings.Join(strings.Fields(str), "")
}

func SpaceStringsBuilder(str string) string {
    var b strings.Builder
    b.Grow(len(str))
    for _, ch := range str {
        if !unicode.IsSpace(ch) {
            b.WriteRune(ch)
        }
    }
    return b.String()
}

func BenchmarkSpaceMap(b *testing.B) {
    for n := 0; n < b.N; n++ {
        SpaceMap(data)
    }
}

func BenchmarkSpaceFieldsJoin(b *testing.B) {
    for n := 0; n < b.N; n++ {
        SpaceFieldsJoin(data)
    }
}

func BenchmarkSpaceStringsBuilder(b *testing.B) {
    for n := 0; n < b.N; n++ {
        SpaceStringsBuilder(data)
    }
}

I found the simplest way would be to use strings.ReplaceAll like so:

randomString := "  hello      this is a test"
fmt.Println(strings.ReplaceAll(randomString, " ", ""))

>hellothisisatest

Playground

From rosettacode.org :

You can find this kind of function :

func stripChars(str, chr string) string {
    return strings.Map(func(r rune) rune {
        if strings.IndexRune(chr, r) < 0 {
            return r
        }
        return -1
    }, str)
}

So, simply replacing chr by " " here should be enough to do the trick and remove the whitespaces.

Beware that there are other kind of whitespaces defined by unicode (like line break, nbsp, ...), and you might also want to get rid of those (especially if you're working with external data you don't really have control over)

This would be done that way:

func stripSpaces(str string) string {
    return strings.Map(func(r rune) rune {
        if unicode.IsSpace(r) {
            // if the character is a space, drop it
            return -1
        }
        // else keep it in the string
        return r
    }, str)
}

Then simply apply to your string. Hope it works, didn't test.