let speed = 2;
    let lastPaintTime = 0;
    
    //Game functions
    function main(ctime) {
      window.requestAnimationFrame(main);
      if ((ctime - lastPaintTime) / 1000 < 1 / speed) {
        return;
      }
      lastPaintTime = ctime;
      gameEngine();
    }
    
    //Main logic starts here
    window.requestAnimationFrame(main);
    

1) window.requestAnimationFrame(main): It calls main function.

2) At the very first line of main function, it again calls main function. So the control should go to main function and forever it should keep calling itself.

3) The if condition should never be checked.

But I asked chatGPT, and it says that if condition will be executed. https://imgur.com/a/eDRS8N5

It says that it doesn't immediately call the main function but schedule/queue it.

What's this behaviour called in Javascript language? Where can I read more about it. Is this common for every programming language?

Things I've read from chatGPT

requestAnimationFrame is a method that schedules a function to be called before the next repaint of the browser window. It does not immediately call the function, but rather adds it to a queue of functions to be called at a later time. This allows the browser to update the screen at a consistent frame rate, while also allowing other tasks to be performed in between frames.

When window.requestAnimationFrame(main) runs inside the main function, it calls web api which runs outside of main thread and places the callback in queue and then result is obtained, meanwhile parallely other code (code below "window.requestAnimationFrame(main)" are running and hence the "if" parts gets executed.