Refine · 
Refine is a type-refinement / validator combinator library for mixed / unknown values in Flow or TypeScript.
Refine is currently bundled as part of the Recoil Sync package.
Please see the Refine Documentation. To get started learning about Refine, check out the documentation on the core concepts of Utilities and Checkers.
Why would I want to use Refine?
- Refine is useful when your code encounters
unknownTypeScript type ormixedFlow type values and you need to assert those values have a specific static type. - Refine provides an API for building type-refinement helper functions which can validate that an unknown value conforms to an expected type.
- Refine can validate input values and upgrade from previous versions.
Type Refinement Example
Coerce unknown types to a strongly typed variable. assertion() will throw if the input doesn't match the expected type while coercion() will return null.
const myObjectChecker = object({
numberProperty: number(),
stringProperty: optional(string()),
arrayProperty: array(number()),
});
const myObjectAssertion = assertion(myObjectChecker);
const myObject: CheckerReturnType<myObjectChecker> = myObjectAssertion({
numberProperty: 123,
stringProperty: 'hello',
arrayProperty: [1, 2, 3],
});Backward Compatible Example
Using match() and asType() you can upgrade from previous types to the latest version.
const myChecker: Checker<{str: string}> = match(
object({str: string()}),
asType(string(), str => ({str: str})),
asType(number(), num => ({str: String(num)})),
);
const obj1: {str: string} = coercion(myChecker({str: 'hello'}));
const obj2: {str: string} = coercion(myChecker('hello'));
const obj3: {str: string} = coercion(myChecker(123));JSON Parser Example
Refine wraps JSON to provide a built-in strongly typed parser.
const myParser = jsonParser(
array(object({num: number()}))
);
const result = myParser('[{"num": 1}, {"num": 2}]');
if (result != null) {
// we can now access values in num typesafe way
assert(result[0].num === 1);
} else {
// value failed to match parser spec
}Usage in Recoil Sync
The Recoil Sync library leverages Refine for type refinement, input validation, and upgrading types for backward compatibility. See the recoil-sync docs for more details.
Installation
Refine is currently bundled as part of the Recoil Sync package.
Contributing
Development of Recoil happens in the open on GitHub, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving Recoil.
License
Recoil is MIT licensed.