What would be the most elegant solution to find all unique first level entries inside a multidimensional javascript array? There is only one important rule: the order of the entries is important only on the first level, but not important on the second level
For example, for the following array the script should return 4 unique entries (the first, the third, the fourth and the fifth):
[
[ [],[22],[1,13,17],[12],[] ],
[ [],[22],[17,13,1],[12],[] ],
[ [],[12],[1,13,17],[22],[] ],
[ [11],[12],[13],[14],[15] ],
[ [15],[14],[13],[12],[11] ]
]
PS. jQuery can be used as well.
If you're not all that worried about performance and just need something that works, you could use the constant depth you mentioned along with the string representation as a "fingerprint" of sorts (akin to Java's hashcode).
Then you use a Set to keep track of items you've not seen before, and add only those that are new.
function getUnique(rows) {
let unique = new Set();
let results = [];
for (let row of rows) {
// Fingerprint is the string representation of the row,
// with the inner-level sorted (as order doesn't matter).
// E.g., fingerprint of [ [8], [3, 2, 1], [9] ] is '[[8],[1,2,3],[9]]'
let fingerprint = JSON.stringify(row.map((cells) => {
return cells.concat().sort(); // Use concat to avoid sorting in place.
}));
// If we haven't seen this fingerprint before,
// add to the filter and the results list.
if (!unique.has(fingerprint)) {
unique.add(fingerprint);
results.push(row);
}
}
return results;
}
This, for example, will come up with...
> x = [
... [ [8], [3, 2, 1], [9] ],
... [ [7], [8, 3, 9], [1, 2] ],
... [ [8], [1, 2, 3], [9] ],
... ];
> getUnique(x);
[ [ [ 8 ], [ 3, 2, 1 ], [ 9 ] ],
[ [ 7 ], [ 8, 3, 9 ], [ 1, 2 ] ] ]
Obviously if your inner values are non-primitives (objects, arrays, etc) then this will fall over, but if you're dealing with numbers like your example, it should be fine.