javascript - 如何为html类添加事件监听器？

Question

如果我有这样的 HTML:

<a href="#" class="movieImg"><div class="previewBulk"></div></a>
<a href="#" class="movieImg"><div class="previewBulk"></div></a>

和这样的 Javascript:

var movie = document.getElementsByClassName("movieImg");
var preview = document.getElementsByClassName("preview");

有什么方法可以addEventListener 2 movie a 标签和预览div 标签吗？我尝试循环，但是当我做类似的事情时:

for(var i = 0, j=movie.length; i<j; i++){
 movie[i].style.left = 100;
 preview[i].style.left = 100;
}

我收到 Uncaught TypeError: Cannot read property 'style' of undefined。

preview改为previewBulk后还是报错，其实我的代码是这样的

(function(){
        var movie = document.getElementsByClassName("movieImg"),
        preview = document.getElementsByClassName("previewBulk");
        //result = [];

        for(var i = 0, j=movie.length; i<j; i++){
            movie[i].addEventListener("mouseover", function(){

                preview[i].style.left = ((movie[i].offsetWidth-preview[i].offsetWidth)/2)+20;
                preview[i].style.top = -(movie[i].offsetHeight+preview[i].offsetHeight);
                preview[i].style.visibility = "visible";
            });

            movie[i].addEventListener("mouseout", function(){
                preview[i].style.visibility = "hidden";
            });
        }
    }());

Answer 1

document.getElementsByClassName 不返回数组。它返回一个像 XML 文件一样遍历的节点列表。

    <a href="#" class="movie"><div class="previewBulk"></div></a>
    <a href="#" class="movie"><div class="previewBulk"></div></a>

    <script>

    var movie = document.getElementsByClassName("movie");

    for(var i = 0; i<movie.length; i++){
      movie.item(i).style.width = "100px";
    }​

    </script>

参见 jsfiddle:http://jsfiddle.net/Uy5fk/