RequestAnimationFrame & deltaTime inconsistancies

[joda]

requestAnimationFrame(update);

var lastTime = 0;
var deltaTime = 0;

function update(timeStamp) {
  //
  deltaTime = timeStamp - lastTime;
  lastTime = timeStamp;
  //
  requestAnimationFrame(update);
}

I'm building an html5 browser game (without phaser or pixi) I'm having problems with getting consistent deltaTimes with this very simple example.

I get different results based on what platform I use:

my PC: ~16

my iPhone ~11

my Mac using Firefox: 24-27

This obviously has a giant impact on how the game displays. What am I doing wrong? Tried searching around, but can't find any answers.

What can I do to get consistent deltaTimes?

[joda]

Never mind. The problem was within my own drawing code, not the deltaTime.

[SanCoca]

What was it that caused inconsistencies?