naive URI text fragment javascript function

textFragment.js

textFragment("foo bar hello spatial world flop flap", '#:~:text=hello,world')  
// hello spatial world

textFragment("foo bar hello spatial world flop flap", '#:~:text=hello spatial,flap')  
// hello spatial world flop flap

// naive implementation: this only supports the main usecase: begin/end
var textFragment = function(text, fragment) {
  if (!fragment.match(/^#:~:text=/)) return text;
  fragment = fragment.replace(/^#:~:text=/, ''); // remove prefix

  const parts = fragment.split(',');
  const start = decodeURIComponent(parts[0] || '');
  const stop = decodeURIComponent(parts[1] || '');

  // Build regex dynamically, escape special characters
  const escapeRegExp = s => s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
  const regex = new RegExp(
    escapeRegExp(start) + '(.*?)' + escapeRegExp(stop),
    's' // 's' flag makes '.' match newline too
  );
  const match = text.match(regex);

  if ( text.match(regex) ) return match[0]
  if (start) {
    const startIndex = text.indexOf(start);
    if (startIndex >= 0) return text.slice(startIndex);
  }
  return text; // fallback
};