Javascript random on array without repeat [duplicate]

Answer 1

I have another very small solution:

It copies the array of possible values and removes the ones, that are added to the new array.

function pickFrom(n, list) {
  const copy = Array.from(list);
  return Array.from(Array(n), () => copy.splice(Math.floor(copy.length * Math.random()), 1)[0]);
}

var quiz = [{
  "question": "What is the full form of IP?",
  "choices": ["Internet Provider", "Internet Port", "Internet Protocol"],
  "correct": "Internet Protocol"
}, {
  "question": "Who is the founder of Microsoft?",
  "choices": ["Bill Gates", "Steve Jobs", "Steve Wozniak"],
  "correct": "Bill Gates"
}, {
  "question": "1 byte = ?",
  "choices": ["8 bits", "64 bits", "1024 bits"],
  "correct": "8 bits"
}, {
  "question": "The C programming language was developed by?",
  "choices": ["Brendan Eich", "Dennis Ritchie", "Guido van Rossum"],
  "correct": "Dennis Ritchie"
}, {
  "question": "What does CC mean in emails?",
  "choices": ["Carbon Copy", "Creative Commons", "other"],
  "correct": "Carbon Copy"
}, {
  "question": "wsxwsxwsxwsxwsxwsx?",
  "choices": ["wsx", "edc", "qaz"],
  "correct": "wsx"
}, {
  "question": "qazqazqazqazqazqaz?",
  "choices": ["qaz", "wsx", "edc"],
  "correct": "qaz"
}, {
  "question": "asdasdasdasdasdasd?",
  "choices": ["asd", "qwe", "zxc"],
  "correct": "asd"
}, {
  "question": "zxczxczxczxczxczxc?",
  "choices": ["zxc", "asd", "qwe"],
  "correct": "zxc"
}, {
  "question": "qweqweqweqweqweqwe?",
  "choices": ["qwe", "asd", "zxc"],
  "correct": "qwe"
}];

console.log(pickFrom(3, quiz));

Reduced example:

function pickFrom(n, list) {
  const copy = Array.from(list);
  return Array.from(Array(n), () => copy.splice(Math.floor(copy.length * Math.random()), 1)[0]);
}

list = [1, 2, 3];

console.log("Pick 1:", pickFrom(1, list).toString());
console.log("Pick 2:", pickFrom(2, list).toString());
console.log("Pick 3:", pickFrom(3, list).toString());
console.log("Pick 3:", pickFrom(3, list).toString());
console.log("Pick 3:", pickFrom(3, list).toString());

Answer 2

Just shuffle the question array and pick one after the other. In a simplified version:

var questions = [1,2,3,4,5,6,7,8,9,10];

function shuffle(a) {
  var cidx, ridx,tmp;
  cidx = a.length;
  while (cidx != 0) {
    ridx = Math.floor(Math.random() * cidx);
    cidx--;
    tmp = a[cidx];
    a[cidx] = a[ridx];
    a[ridx] = tmp;
  }
  return a;
}

function* get_one(arr){
  var idx = arr.length;
  while(idx != 0)
    yield arr[idx--];
}

questions = shuffle(questions);
console.log(questions);

var nextq = get_one(questions);
var alen = questions.length -1;
while(alen--)
  console.log(nextq.next().value);

You don't need that fancy generator, you can just get one after the other in a simple loop if you prefer that.

Answer 3

I'd just shuffle this list - then take the first x questions:

var shuffled = quiz.map(x => { return {data: x, srt: Math.random()}})
.sort((a,b) => {return a.srt - b.srt})
.map(x => x.data);

Answer 4

I added a questionCounter variable to be incremented when your ask question function is called. I also changed your if then statement to use the question counter to set the text of your submit button. Live Preview: http://codepen.io/larryjoelane/pen/yeKwqO

JavaScript:

var questionCounter = 0;

var quiz = [{
  "question": "What is the full form of IP?",
  "choices": ["Internet Provider", "Internet Port", "Internet Protocol"],
  "correct": "Internet Protocol"
}, {
  "question": "Who is the founder of Microsoft?",
  "choices": ["Bill Gates", "Steve Jobs", "Steve Wozniak"],
  "correct": "Bill Gates"
}, {
  "question": "1 byte = ?",
  "choices": ["8 bits", "64 bits", "1024 bits"],
  "correct": "8 bits"
}, {
  "question": "The C programming language was developed by?",
  "choices": ["Brendan Eich", "Dennis Ritchie", "Guido van Rossum"],
  "correct": "Dennis Ritchie"
}, {
  "question": "What does CC mean in emails?",
  "choices": ["Carbon Copy", "Creative Commons", "other"],
  "correct": "Carbon Copy"
}, {
  "question": "wsxwsxwsxwsxwsxwsx?",
  "choices": ["wsx", "edc", "qaz"],
  "correct": "wsx"
}, {
  "question": "qazqazqazqazqazqaz?",
  "choices": ["qaz", "wsx", "edc"],
  "correct": "qaz"
}, {
  "question": "asdasdasdasdasdasd?",
  "choices": ["asd", "qwe", "zxc"],
  "correct": "asd"
}, {
  "question": "zxczxczxczxczxczxc?",
  "choices": ["zxc", "asd", "qwe"],
  "correct": "zxc"
}, {
  "question": "qweqweqweqweqweqwe?",
  "choices": ["qwe", "asd", "zxc"],
  "correct": "qwe"
}];

var currentQuestion = Math.floor(Math.random() * quiz.length);



// define elements
var content = $("content"),
  questionContainer = $("question"),
  choicesContainer = $("choices"),
  scoreContainer = $("score"),
  submitBtn = $("submit");


  score = 0,
  askingQuestion = true;

function $(id) { // shortcut for document.getElementById
  return document.getElementById(id);
}

function askQuestion() {

 //increment the counter
    questionCounter++;

  var choices = quiz[currentQuestion].choices,
    choicesHtml = "";

  // loop through choices, and create radio buttons
  for (var i = 0; i < choices.length; i++) {
    choicesHtml += "<input type='radio' name='quiz" + currentQuestion +
      "' id='choice" + (i + 1) +
      "' value='" + choices[i] + "'>" +
      " <label for='choice" + (i + 1) + "'>" + choices[i] + "</label><br>";
  }

  // load the question
  questionContainer.textContent = "Q" + (questionCounter) + ". " +
    quiz[currentQuestion].question;

  // load the choices
  choicesContainer.innerHTML = choicesHtml;

  // setup for the first time
  if (questionCounter === 1) {
    scoreContainer.textContent = "Score: 0 right answers out of " +
      quiz.length + " possible.";
    submitBtn.textContent = "Submit Answer";


  }

}

function checkAnswer() {




  // are we asking a question, or proceeding to next question?
  if (askingQuestion) {
    submitBtn.textContent = "Next Question";
    askingQuestion = false;

    // determine which radio button they clicked
    var userpick,
      correctIndex,
      radios = document.getElementsByName("quiz" + currentQuestion);
    for (var i = 0; i < radios.length; i++) {
      if (radios[i].checked) { // if this radio button is checked
        userpick = radios[i].value;
      }

      // get index of correct answer
      if (radios[i].value == quiz[currentQuestion].correct) {
        correctIndex = i;
      }
    }

    // setup if they got it right, or wrong
    var labelStyle = document.getElementsByTagName("label")[correctIndex].style;
    labelStyle.fontWeight = "bold";
    if (userpick == quiz[currentQuestion].correct) {
      score++;
      labelStyle.color = "green";
    } else {
      labelStyle.color = "red";
    }

    scoreContainer.textContent = "Score: " + score + " right answers out of " +
      quiz.length + " possible.";
  } else { // move to next question
    // setting up so user can ask a question
    askingQuestion = true;
    // change button text back to "Submit Answer"
    submitBtn.textContent = "Submit Answer";
    // if we're not on last question, increase question number
    if (currentQuestion < quiz.length - 1) {
      currentQuestion++;
      askQuestion();
    } else {
      showFinalResults();
    }
  }
}

function showFinalResults() {
  content.innerHTML = "<h2>You've complited the quiz!</h2>" +
    "<h2>Below are your results:</h2>" +
    "<h2>" + score + " out of " + quiz.length + " questions, " +
    Math.round(score / quiz.length * 100) + "%<h2>";
}

window.addEventListener("load", askQuestion, false);
submitBtn.addEventListener("click", checkAnswer, false);

Answer 5

You need to write some logic. Below is one sample example.

    var list = [1, 2, 3, 4, 5];
    var listDone = [];        
    var inProcess = true;
    while(inProcess){
        var randomQuiz = Math.floor(Math.random() * list.length);

        var isDone = false;
        for (var j = 0; j < listDone.length; j++) {
            if (listDone[j] === randomQuiz)
                isDone = true;
        }
        if (!isDone) {
            console.log(list[randomQuiz]);//Display if not Done.
            listDone.push(randomQuiz);
        }

        if (list.length == listDone.length)
            inProcess = false;

    }

Answer 6

Depending on what you're doing at the end of the quiz, the easiest thing might be to just remove the question from the array once it's been answered.