"Like a boss" solution

The condition for n === 1 is actually unnecessary, since if n = 1, triangular(1 - 1) + 1 = triangular(0) + 1 = 0 + 1 = 1.

Indeed, it does call triangular(0), which returns 0, which is added to the recursive summation, causing no change to the value:
triangular(4) =
triangular(3) + 4 =
triangular(2) + 3 + 4 =
triangular(1) + 2 + 3 + 4 =
triangular(0) + 1 + 2 + 3 + 4 =
0 + 1 + 2 + 3 + 4 =
10

i ended up solving it this way, but i don't understand why this doesn't return 0. if we are recursively calling n-1 wont the function continue until n < 1?

A sample of brilliance.

Yeah, really great solution)))