dom的操作要遵守的原则
1.平稳退化
2.分离javascript
3.向后兼容
4.性能考虑
改进后的显示图片方法
function showpic(whichpic){
if(!document.getElementById("placeholder")) return false;
var source=whichpic.getAttribute("href");
var placeholder=document.getElementById("placeholder");
if(placeholder.nodeName!="IMG") return false;
placeholder.setAttribute("src",source);
if(document.getElementById("description")){
var text=whichpic.getAttribute("title")?whichpic.getAttribute("title"):"";
var description=document.getElementById("description");
if(description.firstChild.nodeType==3){
discription.firstChild.nodeValue=text;
}
}
return true;
}
新添加的分离html和javascript方法
function prepareGallery(){
if(!document.getElementById) return false;
if(!document.getElementByTagName) return false;
if(!document.getElementById("imagegallery")) return false;
var gallery=document.getElementById("imagegallery");
var link=gallery.getElementByTagName("a");
for(var i=0; i<link.length ;i++){
link[i].onclick=function(){
return showpic(this) ? false:true;
}
}
}
添加事件的方法
function addLoadEvent(func){
var oldonload=window.onload;
if(typeof window.onload!='function'){
window.onload=func;
}else{
window.onload-function(){
oldonload();
func();
}
}
}