JavaScript & TypeScript

JavaScript this is undefined inside a callback

JavaScript async function returns before expected work finishes

Promise rejection appears without showing the original error

TypeScript says property does not exist even after type checking

TypeScript cannot find declarations for an installed package

TypeScript build passes locally but fails in CI

JavaScript date shows a different day because of timezone conversion

Optional chaining still throws an undefined error

JSON.parse fails even though the response looks like JSON

Array values change unexpectedly after copying an object