如何从javascript中的数组中获取多个随机不同的项目？

Question

function question1(){
    if(sessionStorage.quizCounter == 0){
        var qa0 = qs[Math.floor(Math.random() * 19)];
        document.getElementById('questions_container').innerHTML = qa0[0]

        for (let i = 1; i <= 3; i++) {
            document.getElementById('answers_container').innerHTML += qa0[Math.floor((Math.random() * 2))+1];
        }
    }
}

That's my function, it's supposed to place the first item in the array in a <div id="questions_container"> which works, but the second part - the for loop - doesn't work.

The for loop is supposed to paste the last 3 items randomly in <div id="answers_container"> . And I don't know how to do that beyond the idea. As it stands now it prints duplicates, which I don't want.

qa0[0] is always the question. qa0[1, 2, 3] is always the answers. qa0[] contains always 4 items. I need the first item to always be on qa0[0].

Answer 1

I figured to answer this question in the easiest possible way.

If you dont need to worry about the positions, you can just randomize the data and then remove the N items off the end.

function shuffle(array) {
  array.sort(() => Math.random() - 0.5);
}

This will shuffle your array, essentially randomizing it. You can then pop the items off the end

function randomitems(arr, returnedCount){
    function shuffle(array) {
      array.sort(() => Math.random() - 0.5);
    }
    const clonedData = arr.slice()
    shuffle(clonedData)
    if ( returnedCount === undefined) return clonedData;
    return clonedData.slice(-1 * returnedCount)
}

This will take up some space because I dont want to change the original object.

Smooth, and Quick. No super complex code.

It will return a random list, and it will return only duplicates IF there are duplicates in the base arr. Otherwise, it will maintain uniqueness of array items.

This will return an array of items, you can then loop that list or do whatever you specifically need with the desired results.

If you want to get super Computer Science-y, I can also give a hyper optimized random set, but that wouldn't likely see much in terms of returns until your dataset started to get big.

This would be used in the following case for you:

// This will link all the questions and possible answers together.
qa0 = [question, ans1, ans2, ans3, ans4].
// The next step is that you need to shuffle the answers.
tmpVar = [].concat(qa0[0], randomizeItems(qa0.slice(1))); // no number will just return the shuffled set.
qa0 = tmpVar;  // You could likely just not even use this tmpVar and just do assignment if you really wanted to.

That way, qa0, will have the question be the 0 index, and all items after are shuffled. So it would then look like: qa0 = [ question, ans3, ans1, ans2, ans4];

Answer 2

let myArray = [1, true, "Hello world!"]; // for example

console.log(myArray[Math.floor(Math.random() * myArray.length)]);