touch detection from Modernizr

(function () {
  /**
   * docElement is a convenience wrapper to grab the root element of the document
   *
   * @access private
   * @returns {HTMLElement|SVGElement} The root element of the document
   */

  var docElement = document.documentElement;


  /**
   * A convenience helper to check if the document we are running in is an SVG document
   *
   * @access private
   * @returns {boolean}
   */

  var isSVG = docElement.nodeName.toLowerCase() === 'svg';

  /**
   * getBody returns the body of a document, or an element that can stand in for
   * the body if a real body does not exist
   *
   * @access private
   * @function getBody
   * @returns {HTMLElement|SVGElement} Returns the real body of a document, or an
   * artificially created element that stands in for the body
   */

  function getBody() {
    // After page load injecting a fake body doesn't work so check if body exists
    var body = document.body;

    if (!body) {
      // Can't use the real body create a fake one.
      body = createElement(isSVG ? 'svg' : 'body');
      body.fake = true;
    }

    return body;
  }

  function createElement() {
    if (typeof document.createElement !== 'function') {
      // This is the case in IE7, where the type of createElement is "object".
      // For this reason, we cannot call apply() as Object is not a Function.
      return document.createElement(arguments[0]);
    } else if (isSVG) {
      return document.createElementNS.call(document, 'http://www.w3.org/2000/svg', arguments[0]);
    } else {
      return document.createElement.apply(document, arguments);
    }
  }

  function injectElementWithStyles(rule, callback, nodes, testnames) {
    var mod = 'device';
    var style;
    var ret;
    var node;
    var docOverflow;
    var div = createElement('div');
    var body = getBody();

    if (parseInt(nodes, 10)) {
      // In order not to give false positives we create a node for each test
      // This also allows the method to scale for unspecified uses
      while (nodes--) {
        node = createElement('div');
        node.id = testnames ? testnames[nodes] : mod + (nodes + 1);
        div.appendChild(node);
      }
    }

    style = createElement('style');
    style.type = 'text/css';
    style.id = 's' + mod;

    // IE6 will false positive on some tests due to the style element inside the test div somehow interfering offsetHeight, so insert it into body or fakebody.
    // Opera will act all quirky when injecting elements in documentElement when page is served as xml, needs fakebody too. #270
    (!body.fake ? div : body).appendChild(style);
    body.appendChild(div);

    if (style.styleSheet) {
      style.styleSheet.cssText = rule;
    } else {
      style.appendChild(document.createTextNode(rule));
    }
    div.id = mod;

    if (body.fake) {
      //avoid crashing IE8, if background image is used
      body.style.background = '';
      //Safari 5.13/5.1.4 OSX stops loading if ::-webkit-scrollbar is used and scrollbars are visible
      body.style.overflow = 'hidden';
      docOverflow = docElement.style.overflow;
      docElement.style.overflow = 'hidden';
      docElement.appendChild(body);
    }

    ret = callback(div, rule);
    // If this is done after page load we don't want to remove the body so check if body exists
    if (body.fake) {
      body.parentNode.removeChild(body);
      docElement.style.overflow = docOverflow;
      // Trigger layout so kinetic scrolling isn't disabled in iOS6+
      docElement.offsetHeight;
    } else {
      div.parentNode.removeChild(div);
    }

    return !!ret;
  }

  function isTouch() {
    var bool;
    var prefixes = ' -webkit- -moz- -o- -ms- '.split(' ');

    if (('ontouchstart' in window) || window.DocumentTouch && document instanceof DocumentTouch) {
      bool = true;
    } else {
      // include the 'heartz' as a way to have a non matching MQ to help terminate the join
      // https://git.io/vznFH
      var query = ['@media (', prefixes.join('touch-enabled),('), 'heartz', ')', '{#device{top:9px;position:absolute}}'].join('');
      injectElementWithStyles(query, function(node) {
        bool = node.offsetTop === 9;
      });
    }
    return bool;
  }
})();