Smooth degradation of links, progressive enhancement, and backwards compatibility

1. Smooth degradation
<a href= "http://www.baidu.com/" title= "a Fengxz" onclick= "Poppup (This.getattribute (" href ")); return false;" >fengxz</a>//html

function Poppup (winurl) {
window.open (Winurl);
}//javascript

This link is available even if JavaScript is disabled.

2. Progressive enhancement

<a href= "www.baidu.com" title= "a Fengxz" class= "Poppup" >fengxz</a>//html

Window.onload=preparelink;
function Preparelink () {
var link=document.getelementsbytagname ("a");
for (Var i=0;i<link.length;i++) {
if (Link[i].getattribute ("class") = = = "Poppup") {
link[i].onclick=function{
Poppup (This.getattribute ("href"));
return false;
}
}
}
}
function Poppup (winurl) {
window.open (Winurl);
}//javasript
JavaScript is separated from the HTML document.

3. Backwards compatibility

if (!document.getelementsbytagname ("a")) return false, and so on, check whether the browser supports this method.

Smooth degradation of links, progressive enhancement, and backwards compatibility