DEV Community

Cover image for I learnt to shuffle an array and an important lesson.
Nirmal Krishna
Nirmal Krishna

Posted on


I learnt to shuffle an array and an important lesson.

😏All these years I have faced the constant problem of sorting an array of int, strings, by property value.

😳I have never thought how can I shuffle this sorted array (even unsorted array).

I came across this problem while I was building a Duolingo style Math quiz app. I had to randomize the position of the correct answer in the array of options.

🤔 I pondered over writing some pseudo code for it, I knew it has to do with randomly selecting an index between the boundaries of the array.

😴 Yet as a lazy engineer I googled for it immediately, to see how people do it. I came across Fisher–Yates shuffle algorithm.

for i from n−1 downto 1 do
     j = random integer such that 0 ≤ j ≤ i
     exchange a[j] and a[i]

🤯 It was quite intriguing with its simplicity. I was able to shuffle my options array.
But then I thought,

Would I have come up with similar algo. without google? I do not know but it would have taken some time

😇 I will not be able to solve all problems without taking help. But I should be comfortable to try and solve it, before getting answers from google.

I had to practice on solving problems that make me uncomfortable.

🚩 I need to take on new challenges outside of my fulltime work(codewars, Leetcode, Freecodecamp, #100daysofreact)

The experience of reinventing the wheel is different for every person

The implementation

shuffleOptions = (optionsArr) => {
        var m = optionsArr.length, t, i;
        while (m) {
            i = Math.floor(Math.random() * m--);
            t = optionsArr[m];
            optionsArr[m] = optionsArr[i];
            optionsArr[i] = t;
        return optionsArr;

Amazing visualization + complexity comparison here.

Randomness mentioned here are pseudo randomness

Top comments (0)