om/node_modules/regexp-clone/index.js

var toString = Object.prototype.toString;

function isRegExp (o) {
  return 'object' == typeof o
      && '[object RegExp]' == toString.call(o);
}

module.exports = exports = function (regexp) {
  if (!isRegExp(regexp)) {
    throw new TypeError('Not a RegExp');
  }

  var flags = [];
  if (regexp.global) flags.push('g');
  if (regexp.multiline) flags.push('m');
  if (regexp.ignoreCase) flags.push('i');
  return new RegExp(regexp.source, flags.join(''));
}