How bad is it to add other attribute to an element or what other options are there?

Question

I have an element where I'm already using the rel attribute, but I would also like to add another attribute that I'll be using in JavaScript.

<a href="/" rel="blah" foo="bar">Link</a>

Is it alright to add other attributes? Or is there a better option?

Answer 1

I would use html5 data- attributes. Even if you are not using html 5 you can be sure your work will still work and is futureproof.

e.g

<li class="user" data-city="Boston" data-food="Bacon">

Answer 2

It's okay to add new attributes through JavaScript, but if you add them directly in the source, your markup won't validate. If it's just one more attribute you need, there's a rev attribute just like rel.