function escapeRegExp(string) {
      string = string == null ? '' : String(string);
      return string && (reRegExpChars.lastIndex = 0, reRegExpChars.test(string))
        ? string.replace(reRegExpChars, '\\$&')
        : string;
    }
Escapes the `RegExp` special characters "\", "^", "$", ".", "|", "?", "*",
"+", "(", ")", "[", "]", "{" and "}" in `string`.

@static
@memberOf _
@category String
@param {string} [string=''] The string to escape.
@returns {string} Returns the escaped string.
@example

_.escapeRegExp('[lodash](http://lodash.com/)');
// => '\[lodash\]\(http://lodash\.com/\)'