javascript - From array, generate all distinct, non-empty subarrays, with preserved order

Question

I have an array, with subarrays and need an algorithm that generates all possible distinct combinations of the subarrays. The resultant combinations can be any length. For example, if the Array has 4 subarrays, the first subarray by itself would be a unique and valid resultant combination, as would any other unique combination of any length.

A combination with the sub-array with the same items in a different order would not be considered unique.

let mainArray = [[0.3, 1], [0.5, 2], [0.6, 3], [0.3, 4]]

// Valid resultant combinations:
[[0.3, 1]]
[[0.3, 1], [0.5, 2]]
[[0.3, 1], [0.5, 2], [0.6, 3]]
[[0.3, 1], [0.5, 2], [0.6, 3], [0.3, 4]]
[[0.5, 2]]
[[0.5, 2], [0.6, 3]]
[[0.5, 2], [0.6, 3], [0.3, 4]]
[[0.6, 3]]
[[0.6, 3], [0.3, 4]]
[[0.3, 4]]
[[0.3, 1], [0.6, 3], [0.3, 4]]
[[0.3, 1], [0.5, 2], [0.3, 4]]
[[0.3, 1], [0.3, 4]]
[[0.3, 1], [0.6, 3]]
[[0.5, 2], [0.3, 4]]

// Don’t think I missed any.

Answer 1

For a more convenient handling, you could take an array of indices and write the code for getting all combinations.

Later, you could replace the array with indices by the real values.

This approach works with a recusion which keeps an array of collected items and an index, which points to the handed over array.

At start, you have a standard exit condition of a recusion which checks if the index is greater than possible and adds the collected values to the result set.

The following part calls the function again with the peviously collected value and a new value from the array and an incremented index and with aother call with only a changed index (here, the actual item is not used).

function getCombinations(array) {
    function iter(temp, index) {
        if (index >= array.length) {
            result.push(temp);
            return;
        }

        iter([...temp, array[index]], index + 1);
        iter(temp, index + 1);
    }
    
    var result = [];
    iter([], 0);
    return result;
}

let array = [[0.3, 1], [0.5, 2], [0.6, 3], [0.3, 4]];

console.log('indices')
getCombinations([...array.keys()]).forEach(a => console.log(...a));
console.log('arrays')
getCombinations(array).forEach(a => console.log(...a.map(b => JSON.stringify(b))));

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