How to convert a list of numbers to unique pairs of two

GR8 :

I have a situation where I need to convert a random array of whole numbers of an unknown length, to multiple pairs of 2.

Ex:

var numbers = [1, 5, 0, 7, 5, 5, 1, 7, 5, 1, 2, 1];

-----------------------------------------------------
[[1, 5], [0, 7], [5, 5], [1, 7], [5, 1], [2, 1]]

There are a few constraints that need to follow, such as:

• There should be exactly 6 pairs (each of 2 numbers).
• If there aren't enough numbers in the numbers array to make 6 pairs, then generate a number that is between 1-9.
• Each item in the numbers array can be used only once.
• Each pair must be unique. But e.g [1,2] and [2,1] can be considered different pairs.
• A pair cannot contain [0, 0]

So far, I found a function that can find combinations but it does not ignore an index once it has already used it.

var numbers = [1, 5, 0, 7, 5, 5, 1, 7, 5, 1, 2, 1];

function p(t, i) {
  if (t.length === 2) {
    result.push(t);
    return;
  }
  if (i + 1 > numbers.length) {
    return;
  }

  p(t.concat(numbers[i]), i + 1);
  p(t, i + 1);
}

var result = [];
p([], 0);
console.log(result);

What should I do next?

KooiInc :

Although Nina may be right about OP needing only the first N pairs from an Array of unknown length, here's an extra check for it (and a slightly different approach to the problem):

const nums1 = [1, 5, 0, 7, 5, 5, 1, 7, 1, 5, 1, 5];
const nums2 = [1, 5, 0, 7, 5, 5, 1, 7, 5, 1, 2, 1];
const nums3 = [1, 5, 0, 7, 5, 5, 0, 0, 5, 1, 2, 1, 0, 0, 1, 8];
const nums4 = [1, 5, 0, 7, 1, 6, 5, 5, 0, 0, 5, 8, 8, 5, 5, 1, 2, 1, 0, 0, 1, 8];
const log = pairs => console.log(JSON.stringify(pairs));
log(createPairs(nums1, 6));
log(createPairs(nums2, 6));
log(createPairs(nums3, 6));
log(createPairs(nums4, 5));
log(createPairs(nums4, 5, true));

function createPairs(numbers, len, truncate) {
  let pairs = [];
  let i = 0;
  const existingValues = new Set(['0|0']);
  const randomDigit = n => Math.floor(Math.random() * (n + 1));

  // create and complete array of [len] unique pairs, not being [0, 0]
  while (pairs.length < len) {
    const pair = i + 2 <= numbers.length
      ? numbers.slice(i, i += 2) 
      : [randomDigit(9), randomDigit(9)];
    const pairStr = pair.join(`|`);
    !existingValues.has(pairStr) && pairs.push(pair);
    existingValues.add(pairStr);
  }
  
  return i + 2 < numbers.length && !truncate 
    ? `This would deliver more pairs than desired (${len})` 
    : pairs;
}

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