jquery 返回顶部功能实现方法

(function($){  
$.fn.survey=function(options){ 
var defaults={width:"298",height:"207"}; 
var options=$.extend(defaults,options); 
if($.browser.msie){ 
var ieVersion=parseInt($.browser.version)} 
//建立HTML 
var __feedCreat=function(){ 
var feedHtml=$('<div id="pubFeedBack"></div>'); 
feedHtml.html('<a href="#top" id="backTop"><i></i>u8fd4u56deu9876u90e8</a><a href="#" id="callSurvey"><i></i>u610fu89c1u53cdu9988</a>'); 
$("body").append(feedHtml); 
__ie6Fixed() 
}; 
//绑定事件 
var __initEvent=function(){ 
$(window).resize(function(){ 
var winW=$(this).width(); 
if(winW<=1124){$("#pubFeedBack").hide()} 
else{$("#pubFeedBack").show()} 
}); 
$(window).bind("scroll",function(){ 
if($(this).scrollTop()>50){ 
$("#backTop").fadeIn().css({"display":"block"}) 
} 
else{$("#backTop").fadeOut().css({"display":""})} 
}); 
$("#backTop").bind("click",function(e){ 
e.preventDefault();  
$("html,body").scrollTop(0)}); 
}; 
//回到顶部 
var __tip=function(type,tipText){ 
var surveyTip=$("#D_SurveyTip"),surveyMask=$("#D_SurveyMask"); 
if(!surveyTip||!surveyMask){return} 
surveyTip.removeClass("warning success").addClass(type).html(tipText); 
surveyMask.css("display","block"); 
surveyTip.css("display","block"); 
setTimeout(function(){ 
surveyMask.css("display","none");   surveyTip.css("display","none")},1000) 
}; 
//ie6兼容 
var __ie6Fixed=function(){
if(ieVersion!==6){return} 
var surveyBox=$("#D_SurveyBox"); 
var pubFeedBack=$("#pubFeedBack"); 
if(!surveyBox||!pubFeedBack) 
{ 
return 
} 
$(window).bind("scroll",function(){ 
var h=$(window).height(),st=$(window).scrollTop(),_top=h+st-options.height; var _top1=h+st-pubFeedBack.height()-15;surveyBox.css("top",_top+"px"); 
pubFeedBack.css("top",_top1+"px") 
}) 
}; 
//开始执行 
if(screen.width>=1280) 
{ 
(function(){ 
__feedCreat();  __initEvent()   })() 
} 
} 
})(jQuery); 
window.onerror=function(){return false}; 
if($.isFunction($(document).survey)){$(document).survey()} 

#backTop i,#callSurvey i{background:url(survey.png) no-repeat;} 
#pubFeedBack{position:fixed;_position:absolute;right:15px;bottom:15px;width:54px;font-size:12px;}
#backTop,#callSurvey{display:block;width:52px;padding:1px;height:56px;line-height:22px;text-align:center;color:#fff;text-decoration:none;} 
#backTop{display:none;background:#999;} 
#backTop:hover{background:#ccc;zoom:1;text-decoration:none;color:#fff;} 
#backTop i{display:block;width:25px;height:13px;margin:14px auto 8px;background-position:-63px 0;} 
#callSurvey{margin-top:1px;background:#3687d9;} 
#callSurvey:hover{background:#66a4e3;zoom:1;text-decoration:none;color:#fff;} 
#callSurvey i{display:block;width:26px;height:25px;margin:9px auto 0;background-position:0 0;} 
#callSurvey:hover i{background-position:-30px 0;}