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

Kevin Faust
Kevin Faust
15,353 Points
Posted by Kevin Faust
Kevin Faust
15,353 Points

Can someone read my code? im not sure why console says undefined

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

//all the questions and answers
var questions = [
  ["What is 50/2?", "25"]
  ["What OS has a green robot?", "ANDROID"]
  ["What is the capital of South Korea?", "SEOUL"]
] 
//all the variables
var response="";
var answer="";
var numberRight=0;
var correct=[];
var wrong=[];

for (var i=0; i<questions.length; i++) {
  response=prompt[i][0];
  answer=[i][1];
  if (response.toUpperCase()===answer) {
    numberRight += 1;
    correct.push(questions[i][0]);
  }
  else {
    wrong.push(questions[i][0]);
}
}
//now correct has an array of the correct questions and wrong has an array of wrong questions

//create an ordered list of each array

for (var i =0; i<correct.length;i++) {
  var completeCorrect = "<ol>";
  completeCorrect += "<li>" + correct[i] +"<li>";
  completeCorrect += "</ol>";
}

for (var i =0; i<wrong.length;i++) {
  var completeWrong = "<ol>";
  completeWrong += "<li>" + wrong[i] +"<li>";
  completeWrong += "</ol>";
}
//display how many user got right
print(numberRight);

//display the correct and wrong
print("You got these questions correct: "+ completeCorrect );
print("You got these questions correct: "+ completeWrong);

The error that javascript is giving me is that: Uncaught TypeError: Cannot read property 'SEOUL' of undefined. but my SEOUL is in quotes so im not sure why it's saying it's undefined. also im not sure if i got my ending part right. i want to take everything pushed into the 2 arrays (correct and wrong) and organize them into another variable as an ordered list (completeCorrect and completeWrong). i also think i can use a function somewhere but i cant seem to figure out where.

Any help would be greatly appreciated. Cheers

4 Answers

Philip G
Philip G
14,600 Points
Philip G
Philip G
14,600 Points

You declared the array indexes without refering to the array. This should finally work:

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

//all the questions and answers
var questions = [
  ["What is 50/2?", "25"],
  ["What OS has a green robot?", "ANDROID"],
  ["What is the capital of South Korea?", "SEOUL"]
] 
//all the variables
var response="";
var answer="";
var numberRight=0;
var correct=[];
var wrong=[];

for (var i=0; i<questions.length; i++) {
  response=prompt(questions[i][0]);
  answer=questions[i][1];
  if (response.toUpperCase()===answer) {
    numberRight += 1;
    correct.push(questions[i][0]);
  }
  else {
    wrong.push(questions[i][0]);
}
}
//now correct has an array of the correct questions and wrong has an array of wrong questions

//create an ordered list of each array

for (var i =0; i<correct.length;i++) {
  var completeCorrect = "<ol>";
  completeCorrect += "<li>" + correct[i] +"<li>";
  completeCorrect += "</ol>";
}

for (var i =0; i<wrong.length;i++) {
  var completeWrong = "<ol>";
  completeWrong += "<li>" + wrong[i] +"<li>";
  completeWrong += "</ol>";
}
//display how many user got right
print(numberRight);

//display the correct and wrong
print("You got these questions correct: "+ completeCorrect );
print("You got these questions correct: "+ completeWrong);
Gabor Salacz
Gabor Salacz
9,020 Points
Gabor Salacz
Gabor Salacz
9,020 Points 
function print(message) {
  document.write(message);
}

//all the questions and answers
var questions = [
  ["What is 50/2?", "25"],
  ["What OS has a green robot?", "ANDROID"],
  ["What is the capital of South Korea?", "SEOUL"]
]; 
//all the variables
var response="";
var answer="";
var numberRight=0;
var correct=[];
var wrong=[];

for (var i=0; i<questions.length; i++) {
  response=prompt(questions[i][0]);
  answer=questions[i][1];
  if (response.toUpperCase()===answer) {
    numberRight += 1;
    correct.push(questions[i][0]);
  }
  else {
    wrong.push(questions[i][0]);
}
}
//now correct has an array of the correct questions and wrong has an array of wrong questions

//create an ordered list of each array

var completeCorrect = "<ol>";
for (var i =0; i<correct.length;i++) {
  completeCorrect += "<li>" + correct[i] +"</li>";
}
completeCorrect += "</ol>";

var completeWrong = "<ol>";
for (var i =0; i<wrong.length;i++) {
  completeWrong += "<li>" + wrong[i] +"</li>";
}
completeWrong += "</ol>";

//display how many user got right
print("Total CORRECT answers: " + numberRight + "<br><br>");

//display the correct and wrong
print("You got these questions correct: "+ completeCorrect );
print("You got these questions incorrect: "+ completeWrong);

There were multiple issues in the code:

  • missing commas between the arrays inside the questions array,
  • the prompt didn't use the questions array at all (the same mistake when assigning value to the answer variable),
  • when creating the completeCorrect and completeWrong strings, the starting and ending <ol> tags must be added once (so you must take them out of the loop),
  • when printing the numberRight value, there were no space / linebreak between it and the next text that gets printed after.

Hopefully this is what you were going after :) Cheers and keep up the good work;

Gabor.

Philip G
Philip G
14,600 Points
Philip G
Philip G
14,600 Points

You have to separate the questions array with commas. This code should work:

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

//all the questions and answers
var questions = [
  ["What is 50/2?", "25"],
  ["What OS has a green robot?", "ANDROID"],
  ["What is the capital of South Korea?", "SEOUL"]
] 
//all the variables
var response="";
var answer="";
var numberRight=0;
var correct=[];
var wrong=[];

for (var i=0; i<questions.length; i++) {
  response=prompt[i][0];
  answer=[i][1];
  if (response.toUpperCase()===answer) {
    numberRight += 1;
    correct.push(questions[i][0]);
  }
  else {
    wrong.push(questions[i][0]);
}
}
//now correct has an array of the correct questions and wrong has an array of wrong questions

//create an ordered list of each array

for (var i =0; i<correct.length;i++) {
  var completeCorrect = "<ol>";
  completeCorrect += "<li>" + correct[i] +"<li>";
  completeCorrect += "</ol>";
}

for (var i =0; i<wrong.length;i++) {
  var completeWrong = "<ol>";
  completeWrong += "<li>" + wrong[i] +"<li>";
  completeWrong += "</ol>";
}
//display how many user got right
print(numberRight);

//display the correct and wrong
print("You got these questions correct: "+ completeCorrect );
print("You got these questions correct: "+ completeWrong);
Kevin Faust
Kevin Faust
15,353 Points
Kevin Faust
Kevin Faust
15,353 Points

Hey Philip. Thanks for the reply. However now it's showing a new error: Uncaught TypeError: Cannot read property '0' of undefined

I don't really understand what this means