页面刷新的时候记住滚动条的位置

window.onbeforeunload = function() {
    var scrollPos;
    if(typeof window.pageYOffset != 'undefined') {
        scrollPos = window.pageYOffset;
    } else if(typeof document.compatMode != 'undefined' &&
              document.compatMode != 'BackCompat') {
        scrollPos = document.documentElement.scrollTop;
    } else if(typeof document.body != 'undefined') {
        scrollPos = document.body.scrollTop;
    }
    document.cookie = "scrollTop=" + scrollPos; //存储滚动条位置到cookies中
};
window.onload = function() {
    if(document.cookie.match(/scrollTop=([^;]+)(;|$)/) != null) {
        var arr = document.cookie.match(/scrollTop=([^;]+)(;|$)/); //cookies中不为空，则读取滚动条位置
        document.documentElement.scrollTop = parseInt(arr[1]);
        document.body.scrollTop = parseInt(arr[1]);
    }
};