Randomising array from a matrix (bidimensional array)

Guillermo Brachetta :

I Currently have the following matrix

const fileName = [
  ["a01", "b01", "c01", "d01", "e01", "f01", "g01", "h01", "i01", "j01", "k01", "l01"],
  ["a02", "b02", "c02", "d02", "e02", "f02", "g02", "h02", "i02", "j02", "k02", "l02"],
  ["a03", "b03", "c03", "d03", "e03", "f03", "g03", "h03", "i03", "j03", "k03", "l03"],
  ["a04", "b04", "c04", "d04", "e04", "f04", "g04", "h04", "i04", "j04", "k04", "l04"],
  ["a05", "b05", "c05", "d05", "e05", "f05", "g05", "h05", "i05", "j05", "k05", "l05"],
  ["a06", "b06", "c06", "d06", "e06", "f06", "g06", "h06", "i06", "j06", "k06", "l06"],
  ["a07", "b07", "c07", "d07", "e07", "f07", "g07", "h07", "i07", "j07", "k07", "l07"],
  ["a08", "b08", "c08", "d08", "e08", "f08", "g08", "h08", "i08", "j08", "k08", "l08"],
  ["a09", "b09", "c09", "d09", "e09", "f09", "g09", "h09", "i09", "j09", "k09", "l09"],
  ["a10", "b10", "c10", "d10", "e10", "f10", "g10", "h10", "i10", "j10", "k10", "l10"],
  ["a11", "b11", "c11", "d11", "e11", "f11", "g11", "h11", "i11", "j11", "k11", "l11"],
  ["a12", "b12", "c12", "d12", "e12", "f12", "g12", "h12", "i12", "j12", "k12", "l12"]
];

and I create a new array with filenames from it randomising 1 item of each subarray using this function:

function randomise() {
  let sequence = fileName.map(option => {
    const random = Math.floor(Math.random() * 11);
    return option[random];
  });
  let randomSelection = sequence.map(createURL);
  function createURL(fileName) {
    return `assets/music/${fileName}.mp3`;
  }
  console.log(randomSelection);
}

So I get an array such as:

["assets/music/f01.mp3", "assets/music/f02.mp3", "assets/music/b03.mp3", "assets/music/k04.mp3", "assets/music/b05.mp3", "assets/music/f06.mp3", "assets/music/i07.mp3", "assets/music/d08.mp3", "assets/music/d09.mp3", "assets/music/g10.mp3", "assets/music/a11.mp3", "assets/music/d12.mp3"]

But I want to rearrange my matrix in this way:

const fileName = [
  ["a01", "a02", "a03", "a04", "a05", "a06", "a07", "a08", "a09", "a10", "a11", "a12"],
  ["b01", "b02", "b03", "b04", "b05", "b06", "b07", "b08", "b09", "b10", "b11", "b12"],
  ["c01", "c02", "c03", "c04", "c05", "c06", "c07", "c08", "c09", "c10", "c11", "c12"],
  ["d01", "d02", "d03", "d04", "d05", "d06", "d07", "d08", "d09", "d10", "d11", "d12"],
  ["e01", "e02", "e03", "e04", "e05", "e06", "e07", "e08", "e09", "e10", "e11", "e12"],
  ["f01", "f02", "f03", "f04", "f05", "f06", "f07", "f08", "f09", "f10", "f11", "f12"],
  ["g01", "g02", "g03", "g04", "g05", "g06", "g07", "g08", "g09", "g10", "g11", "g12"],
  ["h01", "h02", "h03", "h04", "h05", "h06", "h07", "h08", "h09", "h10", "h11", "h12"],
  ["i01", "i02", "i03", "i04", "i05", "i06", "i07", "i08", "i09", "i10", "i11", "i12"],
  ["j01", "j02", "j03", "j04", "j05", "j06", "j07", "j08", "j09", "j10", "j11", "j12"],
  ["k01", "k02", "k03", "k04", "k05", "k06", "k07", "k08", "k09", "k10", "k11", "k12"]
];

I need to randomly select 1 item from each of the indexes of those subarrays, so one random item ending with "1", another ending with "2", etc Could you help me please? Thanks!

Aaron Plocharczyk :

If these are the actual values of the array you're using, you can just loop from 1 through 12 and stick it together with a random character from the string "abcdefghijk" using randojs' rando() function (or otherwise if you prefer).

for(var i = 1; i <= 12; i++){
  console.log("assets/music/" + rando("abcdefghijk") + (i < 10 ? "0" : "") + i + ".mp3")
}

<script src="https://randojs.com/1.0.0.js"></script>

This code uses randojs.com to simplify the randomness and make it easier to read, so if you want to use this code, make sure this is in the head tag of your html document:

<script src="https://randojs.com/1.0.0.js"></script>

---

To answer the second part of your question (which you posted as another answer to this question), you don't need to keep your fileName variable to construct the HTML here if you'd rather not. You can do it like this instead:

var letters = "abcdefghijk";
for(var i = 0; i < letters.length; i++){
    var musicRowID = letters.charAt(i) + "01";
    $("#music-grid").append(`<div id="music-row-${musicRowID}" class="row no-gutters"></div>`);

    for(var j = 1; j <= 12; j++){
        var columnID = letters.charAt(i) + (j < 10 ? "0" : "") + j;
        $(`#music-row-${musicRowID}`).append(`<div class="col-1"><button id="${columnID}" class="btn bar song">${columnID.toUpperCase()}</button></div>`);
    }
}