对象的困惑?

我是在学javascript,这是我看得不太看白的地方,2楼大哥

解决方案 »

  1.   

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    <title>Link Rollover</title>
    <script src="script04.js" language="javascript" type="text/javascript"></script>
    </head>
    <body bgcolor="#FFFFFF">
    <h1><a href="next.html" id="arrow">Next page</a></h1>
    <img src="images/arrow_off.gif" width="147" height="82" id="arrowImg" alt="arrow" />
    </body>
    </html>window.onload = rolloverInit;function rolloverInit() {
    for (var i=0; i<document.links.length; i++) {
    var linkObj =  document.links[i];
    if (linkObj.id) {
    var imgObj = document.getElementById(linkObj.id + "Img");
    if (imgObj) {
    setupRollover(linkObj,imgObj);
    }
    }
    }
    }function setupRollover(thisLink,thisImage) {
    thisLink.imgToChange = thisImage;
    thisLink.onmouseout = rollOut;
    thisLink.onmouseover = rollOver;

    thisLink.outImage = new Image();
    thisLink.outImage.src = thisImage.src; thisLink.overImage = new Image();
    thisLink.overImage.src = "images/" + thisLink.id + "_on.gif";
    }function rollOver() {
    this.imgToChange.src = this.overImage.src;
    }function rollOut() {
    this.imgToChange.src = this.outImage.src;
    }这是翻转器的实现
    thisLink.outImage = new Image();
    这里看不明白,但又想到有个prototype也可以这样,两者不能分清楚的?