How would I add a counter to this in JavaScript

[NeoTheOne]

okay there is my code i just want to how wouldi add a score counter to it. Right now my code is doing this, the function question call is calling the main function which generates a number and if the number matches the condtion it goes and displays the given function. Howver, what i want to do is when it goes and gets the givin function , if the answer is right i want to add 1 to the varible and if its wrong i want to minus one. How can this be done, and is the code so far correct?

var num = 3
var y = 0

for(1=1;i<15;i++){
var x = math.floor(math.random()*num)+1
while (x==y){
var x = math.floor(math.random()*num+1
}
}
}


function question_call(){
main()
if(x == 1){
question1()
}else if(x == 2){
question2()
}else if(x == 3){
question3()
}else if(x == 4){
question4()
}else if(x == 5){
question5()
}else if(x == 6){
question6()
}else if(x == 7){
question7()
}else if(x == 8){
question8()
}else if(x == 9){
question9()
}else if(x == 10){
question10()
}else if(x == 11){
question11()
}else if(x == 12){
question12()
}else if(x == 13){
question13()
}else if(x == 14){
question14()
}else (x == 15){
question15()
}

[NeoTheOne]

okay here is my updated code with what i think is the coutner , but the code doesnt seem to run. please help

<script type="text/javascript">
var score = 0
question_call()
function main(){

var num = 15
var y = 0

	for(1=1;i<15;i++){
	var x = math.floor(math.random()*num)+1
	while (x==y){
	var x = math.floor(math.random()*num+1
			}
		}
	}
	
     function correct(){
	 score = score + 1;
	 }
	 
	 function wrong(){
	 score = score - 1;
	 }
	 
	function question_call(){
	main()
	if(x == 1){
			question1()
		}else if(x == 2){
			question2()
		}else if(x == 3){
			question3()
		}else if(x == 4){
			question4()
		}else if(x == 5){
			question5()
		}else if(x == 6){
			question6()
		}else if(x == 7){
			question7()
		}else if(x == 8){
			question8()
		}else if(x == 9){
			question9()
		}else if(x == 10){
			question10()
		}else if(x == 11){
			question11()
		}else if(x == 12){
			question12()
		}else if(x == 13){
			question13()
		}else if(x == 14){
			question14()
		}else (x == 15){
			question15()
	}
	
	function question1(){
	var question_1 = prompt("Who Is The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
	
		function question2(){
	var question_1 = prompt("Who Is The second Villan In Star Wars ?")
		if(question_1 == "Darth Maul"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question3(){
	var question_1 = prompt("Who Is The4 Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question4(){
	var question_1 = prompt("Who Is The 4Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question5(){
	var question_1 = prompt("Who Is The Vi4llan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question6(){
	var question_1 = prompt("Who Is The Vi4llan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question7(){
	var question_1 = prompt("Who Is 4The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question8(){
	var question_1 = prompt("Who Is The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question9(){
	var question_1 = prompt("Who Is The Villan I4n Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question10(){
	var question_1 = prompt("Who Is The4 Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question11(){
	var question_1 = prompt("Who Is The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question12(){
	var question_1 = prompt("Who Is The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question13(){
	var question_1 = prompt("Who Is The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question14(){
	var question_1 = prompt("Who Is The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			function question15(){
	var question_1 = prompt("Who Is The Villan In Star Wars?")
		if(question_1 == "Darth Vader"){
			correct()
			main()
		}
			else {
				wrong()
				main()
		}
		
			
	
	

</script>