For loop doesn't work in Karel IDE. Can someone explain?

Question

function main(){
   diagonalBeeper();
}

function diagonalBeeper(){
   for (let i = 0; i < 7; i++) {
         move();
         turnLeft();
         putBeeper();
   }
}

I want to make a diagonal beeper line in Karel IDE.. So I made this fn which would repeat itself 7 times but it doesn't work. What's wrong with it?