js中设置屏幕高度及宽度

var screenWidth = document.body.clientWidth+document.body.scrollLeft;

var screenHeight = document.body.clientHeight;

 

var divObj = document.getElementById("元素ID");

divObj.style.display = "block";

var divWidth = divObj.offsetWidth;

var divHeight = divObj.offsetHeight;

 

var left = parseInt((screenWidth - divWidth)/2);
var top = parseInt((screenHeight - divHeight)/2);

divObj.style.left = left+document.body.scrollLeft;
divObj.style.top = top+document.body.scrollTop;