Luhn Algorithm for Luhn validation of credit card number

isValid.js

const isValid = card => {
  const value = card ? card.replace(/\D/g, "") : ''
  if (!value) return false

  let nCheck = 0
  let bEven = false

  for (let n = value.length - 1; n >= 0; n--) {
    const cDigit = value.charAt(n)
    let nDigit = parseInt(cDigit, 10)

  	if (bEven && (nDigit *= 2) > 9) nDigit -= 9

  	nCheck += nDigit
  	bEven = !bEven
  }
  return (nCheck % 10) === 0
}