index.js

var quiz = {
    questions : ["Are u fucked up in life?","No. of days in a week?","No of mounths in a year?","Captian of indian cricket team?","Who played guddu in Mirzapur?"],
    opt1 : ["Yes","2","8","MS Dhoni"],
    opt2 : ["No","7","10","V Kholi"],
    opt3 : ["Not Sure","5","12","Rohit Sharma"],
    opt4 : ["Hapily fucked up","6","11","S Raina"],
    answer : ["Hapily fucked up","7","12","V Kholi","Ali faizal"]
};

var i = 0;

var score = 0;

var ans;

var options = document.forms[0];

document.getElementById("score").innerHTML = 0;
document.getElementById("question").innerHTML = quiz.questions[i];
document.getElementById("op1").innerHTML = quiz.opt1[i];
document.getElementById("op2").innerHTML = quiz.opt2[i];
document.getElementById("op3").innerHTML = quiz.opt3[i];
document.getElementById("op4").innerHTML = quiz.opt4[i];

function changeContent(){
  document.getElementById("score").innerHTML = score;
  document.getElementById("question").innerHTML = quiz.questions[i];
  document.getElementById("op1").innerHTML = quiz.opt1[i];
  document.getElementById("op2").innerHTML = quiz.opt2[i];
  document.getElementById("op3").innerHTML = quiz.opt3[i];
  document.getElementById("op4").innerHTML = quiz.opt4[i];
}

function next(){
  i++;
  jQuery("input:radio").attr('disabled',false);
  jQuery('input:radio').prop('checked', false);
  changeContent();
}

function checkAnswer(event){
    if(quiz.opt1[i]==quiz.answer[i]){
      ans = 1;
    }
    else if(quiz.opt2[i]==quiz.answer[i]){
          ans = 2;
    }
    else if(quiz.opt3[i]==quiz.answer[i]){
          ans = 3;
    }
    else if(quiz.opt4[i]==quiz.answer[i]){
          ans = 4;
    }

    var whichinput = document.getElementsByName("option");
    var len = whichinput.length;
    var checkedinputno;
    var checkedinput;

    for(var b=0; b<len ; b++){
      if(whichinput[b].checked){
        checkedinputno = b;
        checkedinput = whichinput[b];
      }
    }

    if((checkedinputno+1) == ans){
      scoreUpdate();
    }
    jQuery("input:radio").attr('disabled',true);
}

function scoreUpdate(){
  score++;
  document.getElementById("score").innerHTML = score;


}