Shuffle nested arrays in Javascript-CodePudding

I'm trying to sort multiple arrays within an array (which also has to be shuffled). A simplified example is:

let toShuffle = [
[1, 2, 3, 4, 5],
[9, 8, 7, 6, 5],
[10, 67, 19 ,27]
...
];

const shuffled = shuffle(toShuffle);

// outout would look something like:
// [
//   [8, 6, 5, 7, 9],
//   [4, 3, 1, 5, 2],
//   [19, 26, 10, 67],
//   ...
// ]

This needs to be flexible, so any number of arrays with any amount of values should be valid.

Here is what I've tried:

function shuffle(a) {
  for (let e in a) {
    if (Array.isArray(a[e])) {
      a[e] = shuffle(a[e]);
    } else {
      a.splice(e, 1);
      a.splice(Math.floor(Math.random() * a.length), 0, a[e]);
    }
  }

  return a;
}

console.log("Shuffled: "   shuffle([
  [1, 2, 3, 4, 5],
  [5, 4, 3, 2, 1]
]))

But it's not working as intended. Is their an easier way to do this? Or is my code correct and just buggy.

CodePudding user response：

You almost got it. The problem is that you are removing one item from an array, instead of capturing the removed item and them placing in a random position:

let toShuffle = [
[1, 2, 3, 4, 5],
[9, 8, 7, 6, 5],
[10, 67, 19 ,27]
];

function shuffle(a) {
  a = [...a]; //clone array
  for (let e in a) {
    if (Array.isArray(a[e])) {
      a[e] = shuffle(a[e]);
    } else {
      a.splice(~~(Math.random() * a.length), 0, a.splice(e, 1)[0]);
    }
  }

  return a;
}

console.log(JSON.stringify(shuffle(toShuffle)))
console.log(JSON.stringify(toShuffle))

[EDIT] The original code did not shuffle the parent array, if you need shuffle everything recursively, you can use this:

let toShuffle = [
[1, 2, 3, 4, 5],
[9, 8, 7, 6, 5],
[10, 67, 19 ,27]
];

function shuffle(a) {
  a = a.map(i => Array.isArray(i) ? shuffle(i) : i); //clone array
  a.sort(i => ~~(Math.random() * 2) - 1); //shuffle
  return a;
}

console.log("shuffled", JSON.stringify(shuffle(toShuffle)))
console.log("original", JSON.stringify(toShuffle))

CodePudding user response：

You can use Array.prototype.sort() combined with Math.random():

const toShuffle = [
  [1, 2, 3, 4, 5],
  [9, 8, 7, 6, 5],
  [10, 67, 19 ,27]
]

const shuffle = a => [...a].sort(() => .5 - Math.random())
const result = toShuffle.map(shuffle)

console.log('Shuffled:', JSON.stringify(result))
console.log('To shuffle:', JSON.stringify(toShuffle))