How to add item in array every x items?

Question

How can I add an item every x item in an array? For example I would like to add an item every 10 items in the 3rd position:

const arr = [1,2];
const result = [1,2, item];

or

const arr = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16];
const result = [1,2,item,3,4,5,6,7,8,9,10,11,item,12,13,14,15,16];

Answer 1

You could take a while loop and check the length after taking the starting position and the interval length as increment value.

var array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16],
    pos = 2;
    interval = 10;
    
while (pos < array.length) {
    array.splice(pos, 0, 'item');
    pos += interval;
}

console.log(array);

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