Html5之title吸顶功能

const fixedDom = $("#road-tab"),

          isIos = utils.getMobileType(),

          tabclass = "road-tab-fixed";

        let beforeElementScrollTop = 0;

        let beforeOffsetTop = fixedDom[0].offsetTop;

        //scroll节流

        const throttle = (func,wait,mustRun) => {

          var timeout,

            startTime = new Date();

          return function() {

            var context = this,

              args = arguments,

              curTime = new Date()

            clearTimeout(timeout)

            // 如果达到了规定的触发时间间隔，触发 handler

            if(curTime - startTime >= mustRun){

              beforeElementScrollTop = document.body.scrollTop;

              console.log("beforelementScrollTop----------",document.body.scrollTop);

              func.apply(context,args);

              startTime = curTime

              // 没达到触发间隔，重新设定定时器

            }else{

              timeout = setTimeout(func, wait)

            }

          }

        }

        const winScroll = (e) => {

          const elementScrollTop=document.body.scrollTop;

          console.log('elementScrollTop--------------',elementScrollTop);

          if(beforeElementScrollTop - elementScrollTop <=0){//up

            console.log('up');

            if (beforeOffsetTop - elementScrollTop < 0){

              fixedDom.addClass("road-tab-fixed")

            }

          }else{

            if (beforeOffsetTop - elementScrollTop >= 0){console.log("UUUUUU");

              fixedDom.removeClass("road-tab-fixed")

            }

          }

        };

        $(window).off("scroll").on("scroll", throttle(winScroll,10,100));