const state = Immutable.fromJS({
time: performance.now(),
delta: 0
});
const clock = Rx.Observable
.interval(0, Rx.Scheduler.animationFrame)
.scan(previous => {
const time = performance.now();
return previous.merge({
time,
delta: time - previous.get("time")
});
}, state);
clock.subscribe(state => {
document.body.innerHTML = `${Math.round(state.get("delta") * 1000)}μs`;
});
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