Generate numbers from an array?

Question

JavaScript

Take 15 numbers out of 36 numbers that are not in the array.
You need to take a combination of 15 numbers and form an array of them. The maximum number in the array should not exceed 36.

There is an array:

let arr=[
[1,3,4,5,2,6],
[8,9,10,12,11,13]
]

We need to get a new array of 15 numbers. In which there are no numbers from the array arr and each number does not exceed 36.

How to do this?

Answer 1

We create an intermediate arr2 to store all the values ​​from the main array into it, and then we store in arr3 everything that is less than 37 and is not available in the general array.

let arr=[
[1,3,4,5,2,6],
[8,9,10,12,11,13]
]

let arr2 = [];
let arr3 = [];

for(let i = 0; i < arr.length; i++) {
  arr2 = [...arr2, ...arr[i]];
}

for(let k = 0; k < 37; k++) {
  if (!arr2.includes(k)) {
    arr3.push(k);
  }
}