Your date moves a day because one part of the code uses UTC and another uses local time. Find which step does it, keep calendar days as YYYY-MM-DD strings, and name the time zone when you format.
Replace long lists of positional arguments with one options object, destructured in the parameter list with defaults. Add = {} so a call with no argument doesn't crash, and know that defaults only replace undefined.
The file was loaded as a classic script or CommonJS, where import isn't allowed. The fix in the browser is type="module". In Node it's "type": "module" or .mjs, and recent npm init writes "type": "commonjs" for you.
fetch only rejects when there's no response. A 404 or 500 resolves normally, so check response.ok, add a timeout, and keep the status on the error so the caller can decide what to tell the user.
Install the LTS version of Node.js, check the installer's signature, and prove it works in a new terminal with node -v, npm -v and one real install. Plus the fixes for "not recognized" and the wrong version showing.
"Unexpected token in JSON" means JSON.parse got text that isn't JSON. Read the exact message, log the raw text, and match it to one of five causes. Most of the time it's an HTML error or login page.
Five questions a manager would ask about a list of orders, each answered with map, filter, reduce or a plain loop. Real data includes an empty order, and the code has to survive it.
Use npm ci to install exactly what the lock file says and npm install to change it. What each command does, when to use which, and how to fix "npm ci can only install packages when your package.json and package-lock.json are in sync".
Add Vitest to a project you already have and get real tests passing: a pure function with it.each, then an async function that calls fetch, tested with a fake instead of the network.
Keep a counter's value in a closure so nothing outside can set it to -5 or "abc". The pattern, how it compares with a class with
Trace a wrong callback receiver, bind one stable listener, and verify start, stop and restart without duplicate or stale subscriptions.
Six short snippets with setTimeout, promises, await and queueMicrotask. Predict the order, run it, then read why. The one rule: sync code first, then all microtasks, then the next task.