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JavaScript JavaScript Arrays Multidimensional Arrays Build a Quiz Challenge – One Solution

Ziyu Zhang
seal-mask
.a{fill-rule:evenodd;}techdegree
Ziyu Zhang
Front End Web Development Techdegree Student 7,739 Points
Posted by Ziyu Zhang
.a{fill-rule:evenodd;}techdegree
Ziyu Zhang
Front End Web Development Techdegree Student 7,739 Points

Why doing this will not give me the right result?

Here is my code, I find no matter what answer I gave, the correctAnswer is always 3. I learn that if I correct ' if (answers=quiz[i][1])' to' if (answers==quiz[i][1])', the program run correctly. But it doesn;t make sense why (' if (answers=quiz[i][1])')doesn't work.

const quiz=[
  ['What year is it?','2020'],
  ['What\'s the relative of hamburger','hotdog'],
  ['who is the president of the US?','Donald Trump']
];

for (let i=0;i<quiz.length ;i++){
  let answers=prompt (quiz[i][0]);
  if (answers=quiz[i][1]){
    correctAnswer ++;
  }
}

console.log(correctAnswer);

2 Answers

Marcus Klausen
Marcus Klausen
17,425 Points

Hi Ziyu,

First of all you're setting let answer to equal to the question phrase and not the actual answer. The answer is located at index 1 like this:

let answers=prompt (quiz[i][1]);

On the next line you're setting answer to equal something new, instead of checking if the value actually equals the one contained inside the answer constant.

= is an ansignment operator.

For comparison you need to use == and ===

Perhaps check W3CSchools for more information https://www.w3schools.com/js/js_operators.asp

kevin hudson
PLUS
kevin hudson
Courses Plus Student 11,987 Points
kevin hudson
kevin hudson
Courses Plus Student 11,987 Points

Marcus Klausen , Ziyu Zhang code reference to the 

answer = prompt (quiz[i][0]);

is just fine. This is setting your input to equal the answer at the current iteration.

Ziyu Zhang issue is exactly the single = assignment operator.

This was my solution that works. 

const questions = [

  ['What is the color of an apple?', 'red'],
  ['How many inches in a foot?(number only)', '12'],
  ['What is the color of a banana?', 'yellow']

]
let correct = 0;

for(let i = 0; i < questions.length; i++){
  let answer = prompt(questions[i][0]);
  if(answer){
    answer = answer.toLowerCase();
  }
  if(questions[i][1] === answer){
    correct ++;
  }
}
document.querySelector('main').innerHTML = `<h1>You got ${correct} questions correct </h1>`;