获取浏览器视口大小

window.onload = function() {
    alert(" " + getPageScale().pageWidth + ", height: " + getPageScale().pageHeight);
};

/**
 * 获取浏览器视口大小
 * @return {object} 宽，高
 */
function getPageScale(){
    var pageWidth = window.innerWidth,
        pageHeight = window.innerHeight;

    if (typeof pageWidth !== "number") {
        if (document.compatMode === "CSS1Compat") {
            pageWidth = document.documentElement.clientWidth;
            pageHeight = document.documentElement.clientHeight;
        }else{
            pageWidth = document.body.clientWidth;
            pageHeight = document.body.clientHeight;
        }
    }

    return {pageWidth, pageHeight};
}