JS get random value from array and update array

Question

I need your help on this! I'm generating an array which corresponds to a question number. var arrayCharge = []; for (var i = 2; i <= 45; i++) { arrayCharge.push(i); } then I use this number to append the corresponding question, answer then click. Then I'm getting a new value from the array like this const randomQ = arrayCharge; const random = Math.floor(Math.random() * randomQ.length); It works and a new question is charged but the array is still the same. I've tried this var remQ = arrayCharge.indexOf(randomQ[random]); arrayCharge.splice(remQ,1); But It doesn't work ;-( Thanks a lot for your help. Nicolas Here is the entire code to help comprehension! sorry for that, I should have done it from the begining. Repérez vos messages contraignants - Quiz

ATD · Accepted Answer

Nicolas, this is the sort of thing you should end up with:

// From my library js file
// returns a random number in the given range
function getRandomNumber(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

// Variables for objects that need to be available throughout
let availableQuestions = [];
let rnd = 0;
let counter = 0;

// Populate the question array - how this is done depends on where the question data comes from
function createQuestions() {
  availableQuestions.length = 0;
  for (let i = 1; i <= 10; i++) {
    availableQuestions.push({"questionnumber": i, "question": "Text for question " + i});
  }
}

// Pick a random question and display that to the user
function getRandomQuestion() {
  let osQuestions = availableQuestions.length;
  let qnElement = document.getElementById("questionnumber");
  let qElement = document.getElementById("question");
  let sButton = document.getElementById("submit");
  let rButton = document.getElementById("restart");
  // If there are no more questions, stop
  if (osQuestions == 0) {
    qnElement.innerHTML = "Finished!";
    qElement.innerHTML = "";
    sButton.style.display = "none";
    rButton.style.display = "inline";
  } else {
    // display a sequential question number rather than the actual question number
    counter++;
    rnd = getRandomNumber(0, osQuestions - 1);
    let thisQuestion = availableQuestions[rnd];
    qnElement.innerHTML = "Question: " + counter + " (Actually question: " + thisQuestion.questionnumber + ")";
    qElement.innerHTML = thisQuestion.question;
  }
}

// Process the user's answer and remove the question from the array
function submitAnswer() {
  // ALSO Add in what needs to be done to update backend database etc when the user clicks submit
  availableQuestions.splice(rnd, 1);
  getRandomQuestion();
}

// Reset everything - for testing purposes only
function restart() {
  let qnElement = document.getElementById("questionnumber");
  let qElement = document.getElementById("question");
  let sButton = document.getElementById("submit");
  let rButton = document.getElementById("restart");
  qnElement.innerHTML = "";
  qElement.innerHTML = "";
  sButton.style.display = "inline";
  rButton.style.display = "none";
  // Reset the displayed question number counter
  counter = 0;
  createQuestions();
  getRandomQuestion();
}

// Needed to populate the array and display the first question
function runsetup() {
  createQuestions();
  getRandomQuestion();
}

window.onload = runsetup;

<div id="questionnumber"></div>
<hr>
<div id="question"></div>

<button id="submit" onclick="submitAnswer();">Submit</button>
<button id="restart" onclick="restart();" style="display:none;">Restart</button>

I've included a counter variable so that the user does't see the actual question number - just 1, 2, 3 etc but I've shown the actual question number so that you can see it working

ATD · Answer

Nicolas, this is what I think you should be doing:


// Create the array in whatever way you need to
var arrayCharge = [];
for (var i = 2; i <= 45; i++) {
  arrayCharge.push({"questionnumber": i, "question": "Text of question " + i});
}

// Just confirm the length of the array - should be 44
console.log(arrayCharge.length);
// Generate a random number based on the length of the array
var rnd = Math.floor(Math.random() * arrayCharge.length);

// Get the question at the randomly generated index number
let thisQuestion = arrayCharge[rnd];
// Check that we have a random question
console.log(thisQuestion.questionnumber);
console.log(thisQuestion.question)

// Present the question to the user on the page
// The user completes question and clicks "Submit"

// Now remove the question, using the SAME index number
arrayCharge.splice(rnd,1);
// Check that the array has lost an entry - the size should now be 43
console.log(arrayCharge.length);

JS get random value from array and update array

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