if (!('placeholder' in document.createElement('input'))) { }

var $element = $(this), placeholder = $element.attr('placeholder'); if (placeholder) {     // 文本框ID     var elementId = $element.attr('id');     if (!elementId) {         var now = new Date();         elementId = 'lbl_placeholder' + now.getSeconds() + now.getMilliseconds();         $element.attr('id', elementId);     }     // 添加label标签，用于显示placeholder的值     var $label = $('<label>', {         html: $element.val() ? '' : placeholder,         'for': elementId,         css:             {                 position: 'absolute',                 cursor: 'text',                 color: '#a9a9a9',                 fontSize: $element.css('fontSize'),                 fontFamily: $element.css('fontFamily')             }     }).insertAfter($element);     // 绑定事件     var _setPosition = function () {         $label.css({ marginTop: GetStringNumValue($element.css('marginTop')) + 8 + 'px', marginLeft: '-' + (GetStringNumValue($element.css('width')) - 6) + 'px' });     }     var _resetPlaceholder = function () {         if ($element.val()) { $label.html(null); }         else {             _setPosition();             $label.html(placeholder);         }     }     _setPosition();     $element.on('focus blur input keyup propertychange resetplaceholder', _resetPlaceholder);