scrollTo与border结合使用的小玩意

<div onclick="window.scrollTo(0,0);" style="position:fixed; bottom:0; left:20%; opacity:0.7;z-index:1000;color:#fff;text-align:center; cursor:pointer;">
<span style=" display:inline-block;width:0; height:0;overflow:hidden;font-size:0;line-height: 0; border:150px solid transparent;border-bottom-color:#f00;"></span>
<span style="position:absolute; width:100%;text-align:center; left:0; bottom:4%; font-size:36px; color:#090;">GoToTop</span></div>