I have this string that has illegal chars that I want to remove but I don't know what kind of chars may be present.

I built a list of chars that I want not to be filtered and I built this script (from another one I found on the web).

on clean_string(TheString)
    --Store the current TIDs. To be polite to other scripts.
    set previousDelimiter to AppleScript's text item delimiters
    set potentialName to TheString
    set legalName to {}
    set legalCharacters to {"a", "b", "c", "d", "e", "f", 
"g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r",
"s", "t", "u", "v", "w", "x", "y", "z", "A", "B", "C", "D", "E",
 "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R",
 "S", "T", "U", "V", "W", "X", "Y", "Z", "1", "2", "3", "4", "5",
 "6", "7", "8", "9", "0", "?", "+", "-", "Ç", "ç", "á", "Á", "é",
 "É", "í", "Í", "ó", "Ó", "ú", "Ú", "â", "Â", "ã", "Ã", "ñ", "Ñ",
 "õ", "Õ", "à", "À", "è", "È", "ü", "Ü", "ö", "Ö", "!", "$", "%",
 "/", "(", ")", "&", "€", "#", "@", "=", "*", "+", "-", ",", ".",
 "–", "_", " ", ":", ";", ASCII character 10, ASCII character 13}

    --Whatever you want to eliminate.
    --Now iterate through the characters checking them.
    repeat with thisCharacter in the characters of potentialName
        set thisCharacter to thisCharacter as text
        if thisCharacter is in legalCharacters then
            set the end of legalName to thisCharacter
            log (legalName as string)

        end if
    end repeat
    --Make sure that you set the TIDs before making the
    --list of characters into a string.
    set AppleScript's text item delimiters to ""
    --Check the name's length.
    if length of legalName is greater than 32 then
        set legalName to items 1 thru 32 of legalName as text
    else
        set legalName to legalName as text
    end if
    --Restore the current TIDs. To be polite to other scripts.
    set AppleScript's text item delimiters to previousDelimiter
    return legalName
end clean_string

The problem is that this script is slow as hell and gives me timeout.

What I am doing is checking character by character and comparing against the legalCharacters list. If the character is there, it is fine. If not, ignore.

Is there a fast way to do that?

something like

"look at every char of TheString and remove those that are not on legalCharacters"

?

thanks for any help.