How to remove non-printable characters

Issue

I’m trying to remove non-printable characters from a string in Golang.

https://play.golang.org/p/Touihf5-hGH

invisibleChars := "Douglas​"
fmt.Println(invisibleChars)
fmt.Println(len(invisibleChars))

normal := "Douglas"
fmt.Println(normal)
fmt.Println(len(normal))

Output:

Douglas​
10
Douglas
7

The first string has an invisible char at the end.

I’ve tried to replace non-ASCII characters, but it removes accents too.

How can I remove non-printable characters only?

Solution

Foreword: I released this utility in my github.com/icza/gox library, see stringsx.Clean().

---

You could remove runes where unicode.IsGraphic() or unicode.IsPrint() reports false. To remove certain runes from a string, you may use strings.Map().

For example:

invisibleChars := "Douglas​"
fmt.Printf("%q\n", invisibleChars)
fmt.Println(len(invisibleChars))

clean := strings.Map(func(r rune) rune {
    if unicode.IsGraphic(r) {
        return r
    }
    return -1
}, invisibleChars)

fmt.Printf("%q\n", clean)
fmt.Println(len(clean))

clean = strings.Map(func(r rune) rune {
    if unicode.IsPrint(r) {
        return r
    }
    return -1
}, invisibleChars)

fmt.Printf("%q\n", clean)
fmt.Println(len(clean))

This outputs (try it on the Go Playground):

"Douglas\u200b"
10
"Douglas"
7
"Douglas"
7

Answered By – icza

Answer Checked By – Jay B. (GoLangFix Admin)