Large Combinator for NodeJS

I built this library to combine big array elements. The others libraries freeze when you try to use arrays larger then 30 elements even expanding your nodejs memory --max-old-space-size=8192, you DON'T need to do this on this library.

Installing

npm i combination-large

How to use it

Basic usage

All function will returns a result when it's valid and will return null and no result can be found.

next function is the basic usage, every time you call it the pointer will increment and return the referred combination.

getLastPosition function will give you the latest position of the combination pointer, you can use this number to find a specific combination result.

const combination = require('combination-large');

let Combine = new combination({ list: ['a','b','c','d','e'] });
let combinated, pos;

while(combinated = Combine.next()) {
    pos = Combine.getLastPosition();
    console.log(pos + ' - ', combinated);
}

Result

1 -  [ 'e' ]
2 -  [ 'd' ]
3 -  [ 'c' ]
4 -  [ 'b' ]
5 -  [ 'a' ]
6 -  [ 'd', 'e' ]
7 -  [ 'c', 'e' ]
8 -  [ 'c', 'd' ]
9 -  [ 'b', 'e' ]
10 -  [ 'b', 'd' ]
11 -  [ 'b', 'c' ]
12 -  [ 'a', 'e' ]
13 -  [ 'a', 'd' ]
14 -  [ 'a', 'c' ]
15 -  [ 'a', 'b' ]
16 -  [ 'c', 'd', 'e' ]
17 -  [ 'b', 'd', 'e' ]
18 -  [ 'b', 'c', 'e' ]
19 -  [ 'b', 'c', 'd' ]
20 -  [ 'a', 'd', 'e' ]
21 -  [ 'a', 'c', 'e' ]
22 -  [ 'a', 'c', 'd' ]
23 -  [ 'a', 'b', 'e' ]
24 -  [ 'a', 'b', 'd' ]
25 -  [ 'a', 'b', 'c' ]
26 -  [ 'b', 'c', 'd', 'e' ]
27 -  [ 'a', 'c', 'd', 'e' ]
28 -  [ 'a', 'b', 'd', 'e' ]
29 -  [ 'a', 'b', 'c', 'e' ]
30 -  [ 'a', 'b', 'c', 'd' ]
31 -  [ 'a', 'b', 'c', 'd', 'e' ]

previous function

It will decrement the pointer and return the referred combination.

combinated = Combine.previous();
pos = Combine.getLastPosition();
console.log(pos + ' - ', combinated);

Result

31 -  [ 'a', 'b', 'c', 'd', 'e' ]

get function

Will return an specific combination based on the position you pass as param.

combinated = Combine.get(15);
pos = Combine.getLastPosition();
console.log(pos + ' - ', combinated);

Result

15 -  [ 'a', 'b' ]

range param

You can limit the range of elements on a combination passing range.min and range.max params.

let Combine = new combination({ list: ['a','b','c','d','e'], range: { min: 3, max: 4 } });
let combinated, pos;

while(combinated = Combine.next()) {
    pos = Combine.getLastPosition();
    console.log(pos + ' - ', combinated);
}

Result

1 -  [ 'c', 'd', 'e' ]
2 -  [ 'b', 'd', 'e' ]
3 -  [ 'b', 'c', 'e' ]
4 -  [ 'b', 'c', 'd' ]
5 -  [ 'a', 'd', 'e' ]
6 -  [ 'a', 'c', 'e' ]
7 -  [ 'a', 'c', 'd' ]
8 -  [ 'a', 'b', 'e' ]
9 -  [ 'a', 'b', 'd' ]
10 -  [ 'a', 'b', 'c' ]
11 -  [ 'b', 'c', 'd', 'e' ]
12 -  [ 'a', 'c', 'd', 'e' ]
13 -  [ 'a', 'b', 'd', 'e' ]
14 -  [ 'a', 'b', 'c', 'e' ]
15 -  [ 'a', 'b', 'c', 'd' ]
15 -  [ 'a', 'b', 'c', 'd' ]
15 -  [ 'a', 'b', 'c', 'd' ]

reset function

You can use reset to start over. Combine.reset();

getNumberOfCombinations function

Return the number of possible unique combinations for the given parameters. Combine.getNumberOfCombinations();

Next steps

This library can be optimized splitting the subgroups reducing the number of cycles to find the result, be my guest to fork and send me a pull request.