// IE placeholder
(function($) {
    $.fn.placeholder = function(options) {
        var opts = $.extend({}, $.fn.placeholder.defaults, options);
        var isIE = document.all ? true : false;
        return this.each(function() {
            var _this = this,
                placeholderValue = _this.getAttribute("placeholder"
 
); //快取預設的placeholder值
            if (isIE) {
                _this.setAttribute("value", placeholderValue);
                _this.onfocus = function() {
                    $.trim(_this.value) == placeholderValue ? _this.value = "" : '';
                };
                _this.onblur = function() {
 

                    $.trim(_this.value) == "" ? _this.value = placeholderValue : '';
                };
            }
        });
    };
})(jQuery);
    $('.gInput1,.gInput2,.fInput').placeholder();
    這裡的類名就是input的類名。