處理機制是 cookie 和 onbeforeunload()方法的呼叫

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;
}

window.onload = function() {
    if (document.cookie.match(/scrollTop=([^;]+)(;|$)/) != null) {
        var arr = document
 
.cookie.match(/scrollTop=([^;]+)(;|$)/); //cookies中不為空，則讀取滾動條位置  
        document.documentElement.scrollTop = parseInt(arr[1]);
        document.body.scrollTop = parseInt(arr[1]);
    }
}

頁面載入時只執行onload
頁面關閉時只執行onunload
頁面重新整理時先執行onbeforeunload，然後onunload，最後onload。