JavaScript variable won't increment for condition

Question

Some one please explain how I can get the score variable to have one added to it each time a question is answered correctly. Each time I run it I get a score of zero when I answer correctly. Thanks.

var questions = [
['What is 1+1?', 2],
['What is 2+2?', 4],
['What is 4+4?', 8],
];

var score = 0;

for(var i=0; i<questions.length; i++)
    {
    var response = prompt(questions [i][0]);
    var correctAnswer = questions[i][1];
    if (response === correctAnswer)
    {
      score += 1;

    } 

    }
document.write('Your score is '+score);


function print(message) {
  document.write(message);
}

"correct answers" are Number ... prompt returns a string - the two are never equal ... try var response = Number(prompt(questions [i][0])); — Jaromanda X
– Jaromanda X, Commented Oct 3, 2017 at 3:12
Or var response = +prompt(questions[i][0]);. prompt() returns its response as a String. — StackSlave
– StackSlave, Commented Oct 3, 2017 at 3:24

Shadow Fiend · Accepted Answer · 2017-10-03 03:12:03Z

1

parseInt the result in prompt because you want is a number..

var questions = [
['What is 1+1?', 2],
['What is 2+2?', 4],
['What is 4+4?', 8],
];

var score = 0;

for(var i=0; i<questions.length; i++)
    {
    var response = parseInt(prompt(questions[i][0]));
    var correctAnswer = questions[i][1];
    if (response === correctAnswer)
    {
      score++;

    } 

    }
document.write('Your score is '+score);


function print(message) {
  document.write(message);
}

answered Oct 3, 2017 at 3:12

Shadow Fiend

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Comments

brk · Accepted Answer · 2017-10-03 03:18:07Z

1

It may be because the response from the prompt is a string & you are comparing with number. Used uniary operator(+) to convert into number before comparison

var questions = [
  ['What is 1+1?', 2],
  ['What is 2+2?', 4],
  ['What is 4+4?', 8],
];

var score = 0;

for (var i = 0; i < questions.length; i++) {
  var response = prompt(questions[i][0]);
  var correctAnswer = questions[i][1];
   //CHanged here
  if (correctAnswer === +response) {
    score += 1;
  }
}
document.write('Your score is ' + score);


function print(message) {
  document.write(message);
}

answered Oct 3, 2017 at 3:18

brk

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1 Comment

Shadow Fiend Over a year ago

nice answer.. :)

lex · Accepted Answer · 2017-10-03 03:13:43Z

0

Prompt returns a string, and your answers in the array are stored as numbers. Either change your answers to strings or use == instead of === to check for equality. Using double equals will allow the Javascript engine to be flexible with types.

answered Oct 3, 2017 at 3:13

lex

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