Sort an array randomly in JavaScript

Let's assume that you have the following array:

javascript
let array = [1, 2, 3, 4];

You can sort it randomly by:

javascript
let shuffle = array.map((e, i, a) => {
    
    // Getting a random value between [i, a.length]
    // Math.floor can be translated as ~~
    let j = Math.floor(Math.random() * (a.length - i) + i);
    
    // Switching the elements of positions i & j
    [a[i], a[j]] = [a[j], a[i]];
    
    // Returning current value
    return a[i];
    
});

console.log(shuffle);
// [4, 2, 3, 1]

In one line of code:

javascript
let shuffle = array.map((e, i, a, j = ~~(Math.random() * (a.length - i) + i)) => ([a[i], a[j]] = [a[j], a[i]], a[i]));

Testing the function

Now you need to check if the distribution is uniform. Create a test of the function and generate the random array a several number of times:

javascript
let test = {};

for(let i = 0; i < 10000; i ++){
    
    let array   = [1, 2, 3, 4];
    let shuffle = array.map((e, i, a, j = ~~(Math.random() * (a.length - i) + i)) => ([a[i], a[j]] = [a[j], a[i]], a[i]));
    
    let string  = shuffle.join('');
    
    if(test[string] >= 0) test[string] ++;
    else                  test[string] = 0;
    
}

Here you have the total times an array has been created.

For example, the array [1, 2, 4, 3] has been created 396 times.

console.log(test);
/*
1234: 418
1243: 396
1324: 425
1342: 364
1423: 420
1432: 396
2134: 434
2143: 413
2314: 399
2341: 429
2413: 423
2431: 395
3124: 351
3142: 434
3214: 409
3241: 448
3412: 421
3421: 451
4123: 397
4132: 429
4213: 437
4231: 428
4312: 429
4321: 430
*/

It looks like a uniform distribution, because all the possible results have been created with equal probabilty.