Multiples of 3 or 5

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000.

Comment used to generate the code:

function that returns the sum of all multiples of 3 or 5 below the given number

function sumOfMultiples(number: number): number {

      let sum = 0;

      for (let i = 0; i < number; i++) {

        if (i % 3 === 0 || i % 5 === 0) {

          sum += i;

        }

      }

      return sum;

    }

Thoughts:

This is one that I had been able to solve myself without too much difficulty, I think there is likely a lower O(n) solution to this problem. I did not instruct copilot to find the lowers O(n) solution, so fair enough.