var winWidth=0;
if (window.innerWidth) {
winWidth = window.innerWidth;
}
else if ((document.body) && (document.body.clientWidth)) {
winWidth = document.body.clientWidth;
}
document.getElementById("wzsl").style.width = winWidth + "px";
原文：http://www.cnblogs.com/liuzhixian/p/5685538.html