sum of multiples of 21 code example

Example 1: Sum of all the multiples of 3 or 5

const findSum = n => {
  let countArr = []
  
  for(let i = 0; i <= n; i++) if(i % 3 === 0 || i % 5 === 0) countArr.push(i) 
  return countArr.reduce((acc , curr) => acc + curr)
}
console.log(findSum(5))

Example 2: Sum of all the multiples of 3 or 5

const findSum = n => {
  let countArr = []
  
  for(let i = 0; i <= n; i++) countArr.push(i)
    let finalArr = countArr.map(digit => {
      if(digit % 3 === 0 || digit % 5 === 0) return digit
      else return 0
    }).reduce((acc , curr) => acc + curr)
    
  return finalArr
}
console.log(findSum(10))