But if you're not allowed to use any such libraries, then you would have to rely on the browser's built-in method getAttribute to achieve the functionality.
The below code would alert the class value of 'myElem' in all browser's. But, Internet Explorer would just say 'null'!
var elem = document.getElementById("myElem"); alert(elem.getAttribute("class"));
To make that work in Internet Explorer, change to 'className' and see what happens!
var elem = document.getElementById("myElem"); alert(elem.getAttribute("className"));
Now the above code will work only in Internet Explorer but will fail in all other browsers.
So what's the correct solution that works in all browser? Well, don't use the getAttribute() method at all. Instead, use the property className to get the class attribute value.
Here's the cross-browser solution:
var elem = document.getElementById("myElem"); alert(elem.className);
That should do the trick!