text: function prefx(){
    var prefixes = ['moz', 'ms', 'o', 'webkit'];
   
    if ('hidden' in document) {
      return '';
    }
   
    // Loop through each prefix to see if it is supported.
    for (var i = 0; i < prefixes.length; i++) {
      var testPrefix = prefixes[i] + 'Hidden';
      if (testPrefix in document) {
        return prefixes[i];
      }
    }
   
    return;
  }
  