Every yellow flash is a re-render. Interact with the demo, spot what shouldn't be flashing, then open the solution tab to see the fix.
Exercise 1 of 1
Measure a DOM element in useEffect vs useLayoutEffect. See which phase gives you accurate dimensions before the browser paints.
Measured element
Phase log
❌ Measuring in useEffect
Fires after browser paint. A tooltip or overlay repositioned here causes a visible flash — old position → new position.
Recent measurements
Click the button…