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var ul = document.getElementById('ul') var nextButton = document.getElementById('btnNext'); var quizbox = document.getElementById('questionBox') var opt1 = document.getElementById('opt1') var opt2 = document.getElementById('opt2') var opt3 = document.getElementById('opt3') var opt4 = document.getElementById('opt4') var app={ questions:[ { q:'What is the name of the river', options: ['Danube', 'Niger', 'Congo', 'Limpopo'], answer:1 }, { q:'What is the name of the Deadly virus', options: ['Antrax', 'Killvi', 'Corona', 'Wuhanvi'], answer:2 } ], index:0, load:function(){ if(this.index<=this.questions.length-1){ quizbox.innerHTML=this.index+1 + ". " +this.questions[this.index].q; opt1.innerHTML=this.questions[this.index].options[0]; opt2.innerHTML=this.questions[this.index].options[1]; opt3.innerHTML=this.questions[this.index].options[2]; opt4.innerHTML=this.questions[this.index].options[3]; } else { quizbox.innerHTML="Quiz Completed!"; ul.style.display="none"; nextButton.style.display="none"; } }, next: function(){ this.index++; this.load(); }, check: function(ele){ var id=ele.id.split(''); if(id[id.length-1]==this.questions[this.index].answer){ this.score++; ele.className="correct"; this.scoreCard(); } else{ ele.className="wrong"; } }, preventClick:function(){ for(let i=0; i