string/escape.js

define(['../internal/baseToString', '../internal/escapeHtmlChar'], function(baseToString, escapeHtmlChar) {

  /** Used to match HTML entities and HTML characters. */
  var reUnescapedHtml = /[&<>"'`]/g,
      reHasUnescapedHtml = RegExp(reUnescapedHtml.source);

  /**
   * 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_](https://mths.be/he).
   *
   * Though the ">" character is escaped for symmetry, characters like
   * ">" and "/" don't require escaping in HTML and have no special meaning
   * unless they're part of a tag or unquoted attribute value.
   * See [Mathias Bynens's article](https://mathiasbynens.be/notes/ambiguous-ampersands)
   * (under "semi-related fun fact") for more details.
   *
   * Backticks are escaped because in Internet Explorer < 9, they can break out
   * of attribute values or HTML comments. See [#102](https://html5sec.org/#102),
   * [#108](https://html5sec.org/#108), and [#133](https://html5sec.org/#133) of
   * the [HTML5 Security Cheatsheet](https://html5sec.org/) for more details.
   *
   * 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'
   */
  function escape(string) {
    // Reset `lastIndex` because in IE < 9 `String#replace` does not.
    string = baseToString(string);
    return (string && reHasUnescapedHtml.test(string))
      ? string.replace(reUnescapedHtml, escapeHtmlChar)
      : string;
  }

  return escape;
});