Recording FPS in webGL

Question

I am trying to compare performance for 3d applications on mobile devices. I have a 3d solar system set up in webGL and im trying to record or at least display the FPS. So

Answer 1

Since none of the other answers addressed the "in WebGL" part of the question, I'll add the following important details when measuring FPS in WebGL correctly.

window.console.time('custom-timer-id');    // start timer

/* webgl draw call here */                 // e.g., gl.drawElements();

gl.finish();                               // ensure the GPU is ready

window.console.timeEnd('custom-timer-id'); // end timer

For simplicity I used the console timer. I'm trying to make the point to always use WebGLRenderingContext.finish() to ensure the correct time is measured as all WebGL calls to the GPU are asynchronous!