code: function cloneRegexp(re) {
    const pattern = re.source;
  
    let flags = '';
  
    if (re.global) flags += 'g';
    if (re.multiline) flags += 'm';
    if (re.ignoreCase) flags += 'i';
    if (re.sticky) flags += 'y';
    if (re.unicode) flags += 'u';
  
    return new RegExp(pattern, flags);
  }
docs: Function cloning the given regular expression. Supports `y` and `u` flags
  already.
  
  @param  {RegExp} re - The target regular expression.
  @return {RegExp}    - The cloned regular expression.