js 返回顶部

最直接方式window.scrollTo(0,0)

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function returnTop(){

    var scrollObj={

        scrollTop:0,

        winHeight:window.innerHeight,

        dom:null,

        bodyST:0,

        eleST:0,

        intervalTimer:null,

        init:function(dom){

            this.dom=dom

            let scrollHeight=document.body.scrollTop||document.documentElement.scrollTop;

            this.bodyST=document.body.scrollTop;

            this.eleST=document.documentElement.scrollTop;

            if(scrollHeight>this.winHeight){

                dom.style.display='block'

             }else{

                dom.style.display='none'

            }

                this.scroll()

            },

            scroll:function(){

                var timer='10';

                if(this.dom){

                    var _this=this;

                    this.dom.onclick=function(){

                    _this.intervalTimer=setInterval(function(){

                    let scrollHeight=document.body.scrollTop||document.documentElement.scrollTop;

                    let speed=scrollHeight/2

                    if(_this.bodyST!=0){

                        document.body.scrollTop -=speed

                    }else{

                        document.documentElement.scrollTop -=speed

                    }

                    if(scrollHeight==0){

                        clearInterval(_this.intervalTimer)

                    }

                },timer )

                }

            }

        }

    }

    return scrollObj;

}

window.addEventListener('scroll',function(){

    returnTop().init(document.getElementById('returntop'))

})