Custom Permutation Generator

Usage

1.1. require

const CustomPermutation = require('custom-permutation');

1.2. import

import CustomPermutation from 'custom-permutation';

2. Constructor

CustomPermutation(
    elList:[],
    choices:{ index: [] },
    nonChoices:{ index: [] }
)

3. Usage explanied

example:

CustomPermutation(['a', 'b', 'c'], { '1': ['a', 'b'] }, { '0': ['a'] });

Permutate 3 elements which are "a", "b" and "c" with below rules

choices rule:

{ "1": ["a", "b"] }

At index=1 there can only be the element "a" or "b"

nonChoices rule:

{ "0": ["a"] }

At index=0 there can NOT be the element "a"

Note: given index are considered as 0 based: [index=0, index=1, etc.]

| index | all options | after customization | | :---: | :-----------------: | :-----------------: | | 0 | "a", "b", "c" | "b", "c" | | 1 | "a", "b", "c" | "a", "b" | | 2 | "a", "b", "c" | "a", "b", "c" |

4. Result set explanation:

Let's check all permutations, and see which ones are and are not valid.

| Permutation | Is valid | Violates | Description | | :---------------: | :------: | :--------: | :--------------------------------------------: | | ["a", "b", "c"] | No | nonChoices | first elemen can't be "a" | | ["a", "c", "b"] | No | nonChoices | first elemen can't be "a" | | ["b", "a", "c"] | Yes | - | - | | ["b", "c", "a"] | No | choices | second element is asked to be "a" or "b" | | ["c", "a", "b"] | Yes | - | - | | ["c", "b", "a"] | Yes | - | - |

So there are just 3 results that chould be generated with these parameters.

5. Complete example

5.1. Create object from CustomPermutation class

let customPerm = new CustomPermutation(['a', 'b', 'c'], { '1': ['a', 'b'] }, { '0': ['a'] });

5.2. Get next value

5.2.1. With next

let next = customPerm.next();

while (next) {
  console.log(next);
  next = customPerm.next();
}

5.2.2. With generator

let generator = customPerm.generator();
let next = generator.next();

while (!next.done) {
  console.log(next.value);
  next = generator.next();
}

Output:

["b", "a", "c"]
["c", "a", "b"]
["c", "b", "a"]

Fixed bugs

11.06.2026 - Better typing implemented and more test coverage added. 23.09.2024 - Edge cases are handled and the codespace is simplified. 25.09.2023 - unChoices did not reflect always, fixed now.