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JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Build a Quiz Challenge, Part 1 Solution

I'm getting "You got Nan questions right". Not sure why...

var questions = [ ['How many states are in the US?', 50], ['How many PlayStations have been made?', 4], ['How many ears does Java have?', 2] ];

var correctAnswer; var question; var answer; var response; var html;

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

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

html = "You got " + correctAnswer + " questions right."; print(html);

1 Answer

Steven Parker
Steven Parker
211,090 Points

The variable "correctAnswer" is declared but has no value assigned when math is performed on it ("correctAnswer += 1"). Math involving an undefined value produces "NaN" (Not a Number).

An easy fix is to initialize the variable when it is declared: ("var correctAnswer = 0;").

Oh wow, I would have never guessed that. Very good to know! thank you!