Combination problem – Given two integers n and k, write a program to return all possible combinations of k numbers out of 1 2 3 n

I am trying to solve simple algorithm using JS:

Given two numbers n and k and you have to find all possible combination of k numbers from 1…n.

Input : n = 5 
        k = 3

Output : 1 2 3 
         1 2 4 
         1 2 5 
         1 3 4 
         1 3 5 
         1 4 5 
         2 3 4 
         2 3 5 
         2 4 5 
         3 4 5 

However, when I tried this code using JS, I am not getting the expected output:

let ans = [],
  arr = [];

function makeCombination(n, k, low = 1) {
  if (k == 0) {
    ans.push(arr);
    console.log(...arr);
    return;
  }

  for (let i = low; i <= n; i++) {
    arr.push(i);
    makeCombination(n, k - 1, i + 1);
    arr.pop();
  }
  return ans;
}

var n = 5;
var k = 3;

makeCombination(n, k);

Output:

1 2 3
1 2 4
1 2 5

Can you please help, why I am not getting the expected output? I would appreciate any of your assistance.

>Solution :

Beside using some other variables outside of the function, you could take a function which returns a single array.

function makeCombination(n, k, i = 1) {
    const result = [];
    while (i <= n - k + 1) {
        if (k === 1) result.push([i]);
        else result.push(...makeCombination(n, k - 1, i + 1).map(a => [i, ...a]));
        i++;
    }
    return result;
}

makeCombination(5, 3).map(a => console.log(...a));

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