解析javascript 实用函数的使用详解

function addBookMark(url, title){
//将网页添加到收藏addBookMark(window.location,document.title)
    if(document.all){
      window.external.addFavorite(url,title);
    }else if (window.sidebar){
      window.sidebar.addPanel(title,url,'');
    }else{
      alert('添加失败');
    }
}  

function setHomepage(obj,url) {
// setHome(this, window.location)
    try {  
        obj.style.behavior = 'url(#default#homepage)';  
        obj.setHomePage(url);  
    } catch (e) {  
        if (window.netscape) {  
            try {  
                netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");  
            } catch (e) {  
                alert('此操作被浏览器拒绝！\n请在浏览器地址栏输入"about:config"并回车\n然后将 [signed.applets.codebase_principal_support]的值设置为"true",双击即可。');  
            }  
            var prefs = Components.classes['@mozilla.org/preferences-service;1'].getService(Components.interfaces.nsIPrefBranch);  
            prefs.setCharPref('browser.startup.homepage', vrl);  
        }  
    }  
}  

function boxMove(box){
//可移动的层
    var w = box.scrollWidth,h = box.scrollHeight;
    var iWidth = document.documentElement.clientWidth;
    var iHeight = document.documentElement.clientHeight;    
    var moveX = 0,moveY = 0,moveTop = 0,moveLeft = 0,moveable = false;
    box.onmousedown = function(e){   
    moveable = true;    
    e = window.event?window.event:e;
    moveX = e.clientX-box.offsetLeft;       
    moveY = e.clientY-box.offsetTop;
    box.style.zIndex++;
    }
    document.onmousemove = function(e){
        if(moveable){
            e = window.event?window.event:e;       
            var x = e.clientX - moveX;
            var y = e.clientY - moveY;
            if ( x > 0 &&( x + w < iWidth) && y > 0 && (y + h < iHeight)){
                box.style.left = x + "px";
                box.style.top = y + "px";
                box.style.margin = "auto";
            }
        }
    }
    document.onmouseup = function (){moveable = false;};
}

function getHtmlRoot(){
/*获得html文档的根元素*/
    if(document.compatMode.toLowerCase()=="css1compat"){
        htmlRoot = document.documentElement;
    }else{
        htmlRoot = document.body;
    }
    return htmlRoot;
}

function showWindow(boxId, closeId, showBg){//弹窗
    htmlRoot = getHtmlRoot();
    box = document.getElementById(boxId);
    boxId = '#' + boxId;
    closeId = '#' + closeId;
    showBox = $(boxId);
    showBox.show();
    z_index = 20;
    moveLeft =  (htmlRoot.clientWidth- box.clientWidth)/2 + htmlRoot.scrollLeft +'px';
    moveTop = (htmlRoot.clientHeight - box.clientHeight)/2 + htmlRoot.scrollTop;+'px';
    showBox.css({position:'absolute', left:moveLeft,zIndex:z_index, top:moveTop});