Performance
The Re Render Cascade From a Context That Changes Every Tick
A context value rebuilt on every render made every consumer re render on every tick, and the consumers included the provider's own parent, so the cascade…
Code Review
Reviewing a useEffect for the Cleanup It Forgot
The listener, the timer and the subscription all outlive the component that created them, and the leak is invisible on the first mount and obvious on the tenth.
Error Autopsy
The Hydration Mismatch That Only Happened With an Ad Blocker
Support got screenshots of a broken header that no one could reproduce, until someone enabled an ad blocker. The client side DOM was being edited after…
Shopify
Hydrogen or Liquid: Which Should Your Shopify Store Run On
Headless Shopify is genuinely better for some stores and a costly mistake for most. Here is how to tell which one you are.
Next.js
Next.js Dynamic Server Usage: The Static-Dynamic Boundary
Your build fails because a page tried to read a header. Here is what triggers dynamic rendering and how to decide what each route should be.
React
Hydration Failed: Every Cause of the Initial UI Mismatch
A complete diagnostic guide to React hydration mismatches: the eight real causes ranked by how often they actually happen, with the fix for each.
React
Too Many Re-renders: Finding the Infinite Loop in React
React caught the loop and stopped it. Here are the five ways to create one and how the Profiler tells you which you have.
React
Why Your useEffect Runs Twice and Why That Is Correct
React Strict Mode deliberately double invokes your effects in development. It is finding a real bug in your code, not creating one.
JavaScript
Cannot Read Properties of Undefined: Finding the Culprit
The error names the property, not the reason. Here is how to work backwards from the message to the function that returned nothing.