Count the number of prime numbers less than a non-negative number, n.
/**
* @param {number} n
* @return {number}
*/
var countPrimes = function(n) {
const notPrimes = new Uint8Array(n);
let count = 0;
for (let i = 2; i < n; i++) {
if (notPrimes[i] === 0) count++;
for (let j = i * i; j < n; j += i) {
notPrimes[j] = 1;
}
}
return count;
};