Multi-line RegExp with comments

regexp.js

function regexp(...args) {
  function cleanup(string) {
    // remove whitespace, single and multi-line comments
    return string.replace(/\s+|\/\/.*|\/\*[\s\S]*?\*\//g, '');
  }

  function escape(string) {
    // escape regular expression
    return string.replace(/[-.*+?^${}()|[\]\\]/g, '\\$&');
  }

  function create(flags, strings, ...values) {
    let pattern = '';
    for (let i = 0; i < values.length; ++i) {
      pattern += cleanup(strings.raw[i]);  // strings are cleaned up
      pattern += escape(values[i]);        // values are escaped
    }
    pattern += cleanup(strings.raw[values.length]);
    return RegExp(pattern, flags);
  }

  if (Array.isArray(args[0])) {
    // used as a template tag (no flags)
    return create('', ...args);
  }

  // used as a function (with flags)
  return create.bind(void 0, args[0]);
}