I'm building a simple quiz app in JavaScript, where users can select answers via radio buttons. When each question is answered, I push their answers to an array. (Week 6 Assignment of <http://javascriptissexy.com/how-to-learn-javascript-properly/>

I'm trying to build a "back" button where users can click back to previously answered questions. How can I have these radio buttons display their previously selected answer, so they don't have to re-answer the questions?