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Flywheel is a lightweight tool to make working with HTML5's requestAnimationFrame simpler.


Setting up a loop

Flywheel takes two arguments:

After setup, it returns an object that can be used to manipulate the loop. By default, the loop is not running; to start it, use the methods from the next section.

    var element = document.getElementsByTagName("canvas")[0]
    function animation_loop(time_delta){
        /* do animation work here */
    var fw = flywheel(animation_loop, element)

Starting, stopping and toggling a loop

    // start and stop  
    // toggle loop on and off 

Changing the callback and element

To change a callback:

    fw.callback = function(time_delta){
        /* do alternative animation work here */

To change an element:

    fw.element = document.getElementById("my_other_canvas")

Time Delta capping:

When a page loses focus or the loop is paused, the gap between frames can be large enough to cause problems in games (especially where acceleration or collision detection is involved). To combat this, flywheel limits the time_delta value passed to the callback ( by default, to 50ms; equivilent to ~20fps ).

To change the cap:

    fw.framerate_cap = 40

Step for debugging:

    // step forwards a frame (assuming a time delta of 16ms; equivilent to ~60fps) 
    // step forwards with a custom time delta. 


Feel free to run the test suite


This software is available under the MIT license.