Function assert

src/modules/jquery.js:987–1003

* Support testing using an element * @param {Function} fn Passed the created element and returns a boolean result

(fn)

     * @param {Function} fn Passed the created element and returns a boolean result
     */
    function assert(fn) {
      var el = document.createElement('fieldset');

      try {
        return !!fn(el);
      } catch (e) {
        return false;
      } finally {
        // Remove from its parent by default
        if (el.parentNode) {
          el.parentNode.removeChild(el);
        }

        // release memory in IE
        el = null;
      }
    }

    /**
     * Returns a function to use in pseudos for input types