链接预览

window.onload = initAll;var xhr = false;var xPos,yPos;function initAll() {        var allLinks = document.getElementsByTagName("a");        for(var i=0;i<allLinks.length;i++) {             allLinks[i].onmouseover = showPreview;}}function showPreview(evt){        getPreview(evt);        return false;}function getPreview(evt){         if(evt) {                  var url = evt.target;        } else {                 evt = window.event;                  var url = evt.srcElement;} //URL保存在evt.target或window.event.srcElement中        xPos = evt.clientX;         yPos = evt.clientY; //获取当前鼠标的XY坐标         if(window.XMLHttpRequest) {                  xhr = new XMLHttpRequest();} else if(window.ActiveXObject) {          try{                  xhr = new ActiveXObject("Microsoft.XMLHTTP");          }         catch(e) {}} //创建xhr对象         if(xhr) {                  xhr.onreadystatechange = showContents;                   xhr.open("GET",url,true);                  xhr.send(null);}         else {                  alert("Sorry,but I couldn't create an XMLHttpRequest");}} //使用xhr必做的三件事情，与服务器通信，异步取得所需文件function showContents() {         var prevWin = document.getElementById("previewWin");         if(xhr.readyState == 4) {                  prevWin.innerHTML = (xhr.status == 200)?xhr.responseText:"There was a problem with the request " + xhr.status;                 prevWin.style.top = parseInt(yPos)+2+"px";                  prevWin.style.left = parseInt(xPos)+2+"px";                  prevWin.style.visibility = "visible";                  prevWin.onmouseout = hidePreview;}} //将xhr.responseText放进innerHTML会告诉浏览器当显示预览窗口时，它应当将这里的内容解释为HTML。function hidePreview(){         document.getElementById("previewWin").style.visibility = "hidden";}