FizzBuzz program (details given) in Javascript

Question

Can someone please correct this code of mine for FizzBuzz? There seems to be a small mistake. This code below prints all the numbers instead of printing only numbers that are not divisible by 3 or 5.

Write a program that prints the numbers from 1 to 100. But for multiples of three, print "Fizz" instead of the number, and for the multiples of five, print "Buzz". For numbers which are multiples of both three and five, print "FizzBuzz".

function isDivisible(numa, num) {
  if (numa % num == 0) {
    return true;
  } else {
    return false;
  }
};

function by3(num) {
  if (isDivisible(num, 3)) {
    console.log("Fizz");
  } else {
    return false;
  }
};

function by5(num) {
  if (isDivisible(num, 5)) {
    console.log("Buzz");
  } else {
    return false;
  }
};

for (var a=1; a<=100; a++) {
  if (by3(a)) {
    by3(a);
    if (by5(a)) {
      by5(a);
      console.log("\n");
    } else {
      console.log("\n");
    }
  } else if (by5(a)) {
    by5(a);
    console.log("\n");
  } else {
    console.log(a+"\n")
  }
}

Answer 1

for (let i = 1; i <= 100; i++) {
    let out = '';
    if (i % 3 === 0) out += 'Fizz';
    if (i % 5 === 0) out += 'Buzz';
    console.log(out || i);
}