Upcast is a lightweight JavaScript library that provides reliable runtime type utilities. It offers three core functions—`type` to identify a value’s true type (distinguishing arrays and null), `is` to test a value against a given type (with convenient aliases), and `to` to sensibly cast values between primitive types such as array, boolean, function, number, object, string, null and undefined. The package is aimed at developers who need consistent, predictable type‑checking and conversion in Node.js or browser JavaScript projects.