YA: Simple Javascript Questionaire Pt2

/*    Simple Javascript Questionaire    */

/*
    In response to a Yahoo Answers Question.
    To be used with: http://pastebin.com/b6U3L4D8
*/

var questions = [];
questions[0] = {'question': 'What is your Age', 'answers': ['13-18','19-24','25-35','35-50','50+'], 'answer': ''}; // Answer Will Hold the User's Selection
questions[1] = {'question': 'What is your favourite color', 'answers': ['Red', 'Orange', 'Yellow', 'Green', 'Blue', 'Purple'], 'answer': ''};
questions[2] = {'question': 'What is your favourite pet', 'answers': ['Dog','Cat','Rodent','Reptile','Fish'], 'answer': ''};


var curQ = 0;
var ques = questions[curQ];
function echo(s){ console.log(s); }
function byId(id){
    return document.getElementById(id);
}
function checkForAnswer(){
    var ab = byId('answersBox');
    var inputs = ab.getElementsByTagName('input');
    var answer = '';
    if(inputs.length === 0){ return true; }
    for(x in inputs){
        if(inputs[x].checked){ answer = inputs[x].value; }
    }
    ques.answer = answer;
    return (answer.length > 0);
}
function switchQ(v){
    if( (checkForAnswer() && v > 0) || v < 0 ){
        curQ += v;
        displayQuestion();
    }else {
        alert("Question Must Be Answered Before Proceeding");
    }
}
function disableEnableBtns(){
    byId('prevQBtn').disabled = (curQ === 0);
    byId('nextQBtn').disabled = ( curQ === (questions.length - 1));
    byId('resultsQBtn').disabled = (curQ !== (questions.length - 1));
}
function displayQuestion(){
    if(curQ < 0) { curQ = 0; }
    if(curQ >= questions.length){ curQ = questions.length - 1;}
    disableEnableBtns();
    ques = questions[curQ]; // Current Question Object
    var qb = byId('questionBox'); // Question Box
    var ab = byId('answersBox'); // Answers Box
    qb.innerHTML = ques.question + '?';
    ab.innerHTML = 'Select One of the follow:<br>';
    for( i in ques.answers){
        ab.innerHTML += '<input type="radio" name="theAnswer" value="' + questions[curQ].answers[i] + '">' + questions[curQ].answers[i] + '<br>';
    }
    /*    Check for a current Answer    */
    if(ques.answer.length > 0){
        ab.innerHTML = ab.innerHTML.split('value="' + ques.answer + '"').join('value="' + ques.answer + '" checked="checked"');
    }
}
function displayResults(){
    if(!checkForAnswer()){
        alert('Please answer the last question before seeing the results');
    }else{
        var html = '';
        for( i=0;i<questions.length;++i){
            html += '<span style="font-weight: bold;">' + questions[i].question + '?</span> ' + questions[i].answer + '<br>';
        }
        byId('questionBox').innerHTML = 'Results';
        byId('answersBox').innerHTML = html;
    }

}
window.onload = function(){ displayQuestion(); }