Using https://github.com/vegardit/haxe-strings

Slug.hx

import hx.strings.Char;
import hx.strings.StringBuilder;
using hx.strings.Strings;

class Slug {
  static final SEPARATE = [
    Char.BACKSPACE,
    Char.TAB,
    Char.LF,
    Char.CR,
    Char.SPACE,
    Char.EXCLAMATION_MARK,
    Char.BRACKET_ROUND_LEFT,
    Char.BRACKET_ROUND_RIGHT,
    Char.COMMA,
    Char.DOT,
    Char.COLON,
    Char.SLASH,
    Char.SEMICOLON,
    Char.LOWER_THAN,
    Char.GREATER_THAN,
    Char.QUESTION_MARK,
    Char.UNDERSCORE,
    Char.PIPE,
    Char.BRACKET_CURLY_LEFT,
    Char.BRACKET_CURLY_RIGHT,
    Char.BACKSLASH,
    Char.DOUBLE_QUOTE,
    Char.ESC,
    Char.HASH,
    Char.SINGLE_QUOTE,
    Char.ASTERISK
  ];

  public static function slug(str: String, separator = '-'): String {
    final parts: Array<String> = [];
    final current = new StringBuilder();
    for (char in str.toLowerCase8().toChars())
      if (SEPARATE.indexOf(char) > -1) {
        if (current.isEmpty()) continue;
        parts.push(current.toString());
        current.clear();
      } else {
        current.addChar(char);
      }
    if (!current.isEmpty()) parts.push(current.toString());
    return parts.join(separator);
  }
}