function escape(string) {
      // reset `lastIndex` because in IE < 9 `String#replace` does not
      string = string == null ? '' : String(string);
      return string && (reUnescapedHtml.lastIndex = 0, reUnescapedHtml.test(string))
        ? string.replace(reUnescapedHtml, escapeHtmlChar)
        : string;
    }
Converts the characters "&", "<", ">", '"', "'", and '`', in `string` to
their corresponding HTML entities.

**Note:** No other characters are escaped. To escape additional characters
use a third-party library like [_he_](http://mths.be/he).

When working with HTML you should always quote attribute values to reduce
XSS vectors. See [Ryan Grove's article](http://wonko.com/post/html-escaping)
for more details.

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

_.escape('fred, barney, & pebbles');
// => 'fred, barney, &amp; pebbles'