Why does this prime-checker work?

Question

The following code correctly determines if a number is prime:

var num = parseInt(prompt("Number:"));
var ans = "prime";

for (var i = 2; i < num; i++) {
  if (num % i === 0) {
    ans = "not prime";
    break;
  }
}
alert(ans);

Why does this code work for an input of "2"?

I thought that an input of 2 would give "not prime", as 2%2===0 would be true.

Answer 1

I thought that an input of 2 would give "not prime", as 2%2===0 would be true.

2 % 2 never happens.

The loop that checks for evenly divisible numbers is:

for (var i = 2; i < num;...

i starts at 2, and num is the user input.

If num is also 2, then the first test of i < num is 2 < 2, which is false. The loop never executes and ans remains "prime".