javascript,_突然忘记这个怎么写了：单元格点击高亮后，然后点击下面的按钮，把高亮部分里面的内容弹出来，javascript

突然忘记这个怎么写了：单元格点击高亮后，然后点击下面的按钮，把高亮部分里面的内容弹出来

问题：单元格点击高亮后，然后点击下面的按钮，把高亮部分里面的内容弹出来
HTML代码

<body>
<table border="1">
    <tr>
        <td>Row 1, cell 1</td>
        <td>Row 1, cell 2</td>
    </tr>
        <tr>
        <td>Row 1, cell 1</td>
        <td>Row 1, cell 2</td>
    </tr>
        <tr>
        <td>Row 1, cell 1</td>
        <td>Row 1, cell 2</td>
    </tr>
</table> 
<button id="button">选好了，点击弹出</button>
</body>

JS代码

<script>
window.onload = function(){
    var aTable = document.getElementsByTagName("table")[0];
    var aTd = aTable.getElementsByTagName("td");
    var oBtn = document.getElementById("button");

    //高亮
    for(var i=0; i<aTd.length; i++){
        aTd[i].onclick = function(){            
            if(this.className){
                this.className = "";
            }else{
                this.className = "actbg";
            }
        }
    }

    //点击按钮
    oBtn.onclick = function () {
        //....
    }
}
</script>

window.onload = function(){
    var aTable = document.getElementsByTagName("table")[0];
    var aTd = aTable.getElementsByTagName("td");
    var oBtn = document.getElementById("btn");

    for(var i=0; i<aTd.length; i++){
        aTd[i].onclick = function(){
            if(this.className){
                this.className = "";
            }else{
                this.className = "changebg";
            }
        }
    }

    oBtn.onclick = function(){
        var a = [];
        var aTdclass = document.getElementsByClassName("changebg");

        for(var i=0; i<aTdclass.length; i++){
            a.push(aTdclass[i].innerHTML);
        }
        alert(a.join(" || "));
    }

}