Simple Example

Towards the top of this page, you saw an example of an animation with circles buzzing around a fixed point. You can also view it in a new window if you want to see it in isolation.

The script for making that animation work looks as follows:

  • HTML
  • JavaScript
This all seems like a lot of code, but don’t worry about all of that for now. Instead, just pay attention to the highlighted lines. In the two highlighted lines, we call requestAnimationFrame with the draw function specified as the callback.


Below is that code with everything extraneous omitted:


function createCircles() {
       .
       .
       .
    requestAnimationFrame(draw);
}
createCircles();
 
function draw() {
      .
      .
      .
    requestAnimationFrame(draw);
}
Notice that you are essentially creating a loop where you are calling the draw function using the requestAnimationFrame, and inside the draw function, you have another requestAnimationFrame call with the same draw function specified. You don’t have to use requestAnimationFrame to make the first call to the draw function. You could have just called draw directly just like I called the animate method a few sections earlier. There is no right or wrong way to do this, but by using requestAnimationFrame even for the initial call, you are deferring when to call the draw method to your browser as opposed to forcing it to be called instantaneously.


Inside the draw method, while this looks like it might cause an infinite loop, your browser knows what to do and ensures that nothing bad like that happens. Don’t try something like this with your own vanilla functions, though :P