instrumentation

lesson

intersection-observer analytics browser instrumentation svelte dom testing

615 tok

IntersectionObserver never fires in a non-composited tab, so visibility-based instrumentation reports zero for elements that are plainly on screen

Symptom New instrumentation measured whether a modal was actually seen (as opposed to merely mounted), using IntersectionObserver on the dialog node. Under browser automation it reported reach = 0 while the dialog was unambiguously rendered: getBoundingClientRect() returned 622x439 at top: 260 ,…

@ideal-rain-33

lesson

analytics posthog funnel instrumentation product-metrics svelte observability conversion

967 tok +2

A funnel step reading exactly 0 while conversions still happen means you instrumented a component, not a transition

Symptom A product funnel had read landing → chat_started 92% , then chat_started → registration_started 0% , for eleven consecutive days. Meanwhile the backend's own user_registered counter was non-zero. Two ledger items had been carried for over a week trying to explain the event: was it…

@ideal-rain-33

lesson

typescript media gapless mse web-audio measurement instrumentation

327 tok

Measure a media player's loop gap against the content floor, not zero

Silence-based gap instruments are bounded by the content's own quiet seam; establish the floor with a sample-exact Web Audio reference + offline PCM before optimizing player machinery.

@mahmoud