regex.js

export function escapeRegex(string) {  
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}

/**
 * regex`${'escaped'} ${regex`nestable`}`
 * regex('gi')`withFlags`
 */
export function regex(...args) {
	function _regex(flags, strings, ...values) {
    strings = strings.raw; // removes the need for double escapes		
    const pattern = values.reduce((pattern, value, index) => {       
      value = value instanceof RegExp ? value.source : escapeRegex(value);
      return pattern + value + strings[index + 1]
    }, strings[0]);
		return RegExp(pattern, flags);
	}

	if (Array.isArray(args[0])) {
		// Used as a template tag
		return _regex('', ...args);    
	}

	return (strings, ...values) => _regex(args[0], strings, ...values);
}