The Valof Book
v0.8.0
Write robust domain logic in TypeScript
just by following the conventions.
The Valof Book is both a guide and a reference. Read it in order to learn the conventions, or use the sidebar to find a specific topic.
Important
Valof is pre-1.0. A minor release can change the API.
Why Valof?
Valof is an opinionated value-object helper for TypeScript that enforces the conventions through types and linting.
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Nominal-ish typing with a phantom brand: TypeScript distinguishes one Val type from another, with nothing to pay at runtime.
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Values as plain data: Vals stay objects, arrays and primitives. They serialize without adapters and fit directly into React and other framework state. No classes, no prototypes.
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Immutability: Vals are immutable. Their types are deeply readonly, and their constructors copy their inputs, so an original reference cannot mutate them.
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No
ascasts in your code: Valof owns the cast required to construct a branded value. -
Companion object: Keep a type’s constructor and functions together without a class. The first Val parameter is inferred.
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“Parse, don’t validate”: Every creation and derivation goes through one
seal. Use any validation library and any Result type. -
Copy only what changes:
patchcopies only the paths it changes. Untouched branches keep their reference identity. -
Rust-like abstractions (experimental):
Enumis a closed set of variants with exhaustivematch.Traitshares behavior across Vals.dynadds dynamic dispatch without classes, holding different types together. -
Built-in linter: Catch convention violations through ESLint, Oxlint or the standalone command.
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Lightweight: Starts from 852 B gzipped, with no runtime dependencies.
For background on individual features, see TypeScript problems Valof addresses.