js去除浏览器默认底图的方法

function addListener(element, type, expression, bubbling) {
bubbling = bubbling || false;
if(window.addEventListener) { // Standard
element.addEventListener(type, expression, bubbling);
return true;
}
else if(window.attachEvent) { // IE
element.attachEvent('on' + type, expression);
return true;
}
else return false;
}
var ImageLoader = function(url){
this.url = url;
this.image = null;
this.loadEvent = null;
};
ImageLoader.prototype = {
load:function(){
this.image = document.createElement_x('img');
var url = this.url;
var image = this.image;
var loadEvent = this.loadEvent;
addListener(this.image, 'load', function(e) {
if(loadEvent != null){
loadEvent(url, image);
}
}, false);
this.image.src = this.url;
},
getImage:function(){
return this.image;
}
};
function loadImage(objId,urls) {
var loader = new ImageLoader(urls);
loader.loadEvent = function(url){
obj = document.getElementByIdx_x(objId);
obj.src = url;
}
loader.load();
}

<img id="loading1″ src="loading.gif" />
<script language="javascript">
loadImage("loading1″,"baidu_logo.gif");
</script>