Unless vs if in Javascript with use of exclamation point?

The code below attempts to print out "is even" for numbers divisible by 2.

Should it not be if (test) then() rather than: if (!test) then(), when condition tested is "n % 2". The code below seems to read "IF numbers are NOT divisible by 2, print out 'number is even' ", which does not seem logical.

More generally speaking, what are the advantages of writing an Unless function over using an If statement in specifying condition, when what we could do is simply write if (!condition)?

Any help is much appreciated.

function unless(test, then) {
  if (!test) then();
}
function repeat(times, body) {
  for (var i = 0; i < times; i++) body(i);
}

repeat(3, function(n) {
  unless(n % 2, function() {
    console.log(n, "is even");
`enter code here`});
// → 0 is even
// → 2 is even