javascript 两种方式实现动态雪碧图

function changePicture() {
    //拿到div对象
    var gallery = document.getElementById("picture_gallery");
    var gallert_img = document.getElementsByTagName("img");

    var atag = document.getElementsByTagName("a");
    for(var i=0 ; ivar current_a = atag[i];
        current_a.onmouseover = function () {
            var text = this.lastChild.nodeValue;
            gallert_img[0].className = "picture_gallery_"+text;  //这个文本前面可是没有.的哦
        }
    }
}


function addClassName(element,value) {
    if(!element.className){
        element.className = value;
    } else {
        element.className += " ";
        element.className += value;
    }
}

方式1 这种方法是利用js去修改img的classname从而调用不同的样式