how do i make it so my object shoots out a projectile on command

ok so i've been trying to find a way that it would shoot out a projectile on command.
what i mean by this is that, my game uses a fire rate system created by @Letti42, you have to hold down the key to make it shoot (you can't just press it once or else it wont shoot), so i thought about a solution. as it turns out i dont know how to make it, that's why im asking.
(ignore the functions that are not relating to the gun's shooting)

 var timer;
  function startShooting(fireRate){
  fireRate = fireRateEach;
  if(timer)return;
  timer = setInterval(function(){
    createBullets();
    loseBullet();
    playSound("gunShot.mp3", false);
  }, fireRate);
 }

 function stopShooting(){
  setTimeout(function() {
    clearInterval(timer);
     timer = 0;
  }, gunWentDown);
 }

 function createBullets(){
   bullet = createSprite(player.x, player.y);
   bullet.setAnimation("bullet");
   bullets.add(bullet);
   bullet.setSpeedAndDirection(8, player.rotation);
   bullet.lifetime = 100;
 }

 function shooting() {
   if (keyDown("space") || keyWentDown("space")) {
      startShooting();
   }
   if (keyWentUp("space") || stage != "game") {
     stopShooting();
   }
 }