Finprim: A Unified Financial Validation Library
A TypeScript library called finprim has been developed to streamline financial validation tasks across multiple platforms and products.
finprim is an MIT-licensed TypeScript library that consolidates financial validation functions such as IBAN, BIC, card, sort code, VAT, routing number, and loan calculations into a single API. The library was developed by Oluwatosin Adelaja, who highlighted that the motivation came from repeated duplication of validation logic across different products at Sprint Technology Solutions. This duplication led to inconsistencies and bugs, such as differing validation rules between the web and mobile versions of an application, causing user frustration and delayed debugging (source ID 1). [1]
Adelaja emphasized that while existing single-purpose packages can be assembled, they often require additional glue code to maintain consistency. finprim's approach is to provide a unified API that ensures the same input and result structures across all validation types. This design eliminates the need for multiple dependencies and reduces the potential for errors during integration (source ID 1). [1]
The library uses branded types to prevent runtime errors caused by unvalidated data being passed into functions expecting validated inputs. This ensures that validation occurs at compile time, preventing issues that could arise during live transactions. finprim does not store, transmit, or process payments, focusing solely on validation and formatting of financial data according to published standards (source ID 1). [1]
Validation rules in finprim are sourced from published standards such as ISO 13616 for IBAN, Luhn algorithm for card numbers, and per-country formats for VAT. The library is tested against known-good and known-bad values from these standards, achieving high test coverage, particularly in core validation modules. Adelaja also noted that maintaining correctness over time involves manual updates to formats as standards evolve, with community contributions helping identify edge cases (source ID 1). [1]
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finprim is an MIT-licensed TypeScript library that provides financial validation and formatting capabilities for IBAN, BIC, card numbers, sort codes, VAT, and loan calculations, all through a single API. It was developed by Oluwatosin Adelaja at Sprint Technology Solutions, where the need for a unified validation system arose from repeated duplication of similar financial validation logic across multiple products. The library was first motivated by the inefficiency of maintaining separate validation implementations for web and mobile platforms, which led to inconsistencies and user frustration during payout flows. The fifth release, version 0.1.4, has been published, and the repository has 81 stars on GitHub. [1]
The project’s scope includes validating and formatting financial data based on published international standards, such as ISO 13616 for IBAN and Luhn algorithm for card numbers. finprim does not store, send, or process payments, and it avoids any network activity, database usage, or telemetry. The library ensures that sensitive financial data is not logged, and it guarantees that inputs are checked against published standards without exposing the actual values. It is designed as a validation and formatting toolkit rather than a full-featured payment processing system. [1]
The library maintains correctness by sourcing its validation rules directly from authoritative specifications, such as country-specific IBAN formats, VAT rules, and card network ranges. Testing is conducted against known-good and known-bad values from these references, ensuring that the library’s behavior aligns with the standards. The test coverage is around 91% of lines and 88% of statements, with the core validation modules achieving 94% line coverage. The library is updated manually as standards evolve, and community contributions help identify edge cases that the author might not encounter. [1]
The project has not yet expanded beyond validation and formatting, and the author has deliberately avoided moving into transaction generation, such as SEPA or ACH file creation. finprim’s long-term goal is to remain a focused validation and formatting toolkit, avoiding the pitfalls of becoming a full-featured payment engine. The current versioning strategy uses 0.1.x, with all five releases being patch updates rather than major version changes. There is no dedicated migration guide, and users are directed to the README and release notes for reference. [1]
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