SIN.js

const MULTIPLIERS = [1, 2, 1, 2, 1, 2, 1, 2, 1];

const isValid = (sin) => {
  if (typeof sin !== 'string' || sin.length !== 9) {
    return false;
  }

  splitedSin = sin.split('').map(Number);
  const digits = splitedSin.reduce((allDigits, val, index) => {
    const result = String(val * MULTIPLIERS[index]).split('');
    return [...allDigits, ...result];
  }, []);
  const key = digits.reduce((sum, digit) => sum + Number(digit), 0);

  return key % 10 === 0;
}

console.log(isValid('046454286'));