fixed

 1 !(function(){
 2     $.fn.affix = function(options){
 3         var defualtOption = {
 4             top:0,
 5             container:$("html, body"),
 6             bottom:0
 7         }
 8         var option = $.extend( defualtOption, options);
 9         var offsetTop = $(this).offset().top;
10         var height = option.container.height();
11         var cOffsetTop = option.container.offset().top;
12         var limmit = height + cOffsetTop - option.bottom;
13         var _this = this;
14         $(window).on("scroll",function(){
15             var scorllTop = $(window).scrollTop();
16             console.log("dddd")
17             console.log(offsetTop)
18             console.log(scorllTop + cOffsetTop)
19             if(offsetTop < scorllTop  && scorllTop < limmit){
20                 if(window.XMLHttpRequest){
21                     $(_this).css({
22                         position:"fixed",
23                         top:0
24                     })
25                 }else{
26                     $(_this).css({
27                         position:"absolute",
28                         top: offsetTop - scorllTop
29                     })
30                 }
31             }else{
32                 $(_this).css({
33                     position:"static"
34                 })
35             }
36         })
37     }
38 })(jQuery)