Ow
Function argument validation for humans
...Built-in predicates cover common constraints, while custom validators can handle application-specific requirements. Failed checks produce descriptive errors intended to make debugging easier than relying on later runtime failures. Ow can also test values without throwing and includes TypeScript type guards that narrow unknown values after successful validation. It works in server, browser, and command-line environments and is aimed at focused runtime checks rather than large schema validation workloads.