panel = document.getElementById("panel");
 div3 = document.getElementById("div3");
 panel.scrollTop = div3.offsetTop; 

3.js平滑滚动div到div3，滚动到居中的位置

var panel = $("#panel");
var div3 = document.getElementById("div3");
panel.animate({
    scrollTop:div3.offsetTop - panel.height()/2
},200);