Package Exports

@bitty/predicate

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Readme

`@bitty/predicate`

Predicate and Refinement types for TypeScript.

🏷 Safe:
- JSDocs and type declarations for IDEs and editor's autocomplete/intellisense.
- Made with TypeScript as strict as possible.
- Unit tests with AVA.

Installation

This library is published in the NPM registry and can be installed using any compatible package manager.

npm install @bitty/predicate --save

# For Yarn, use the command below.
yarn add @bitty/predicate

Getting Stated

It exports Predicate and Refinement types.

Predicate is a function that receives a value and returns a boolean.

import type { Predicate } from '@bitty/predicate';

function checkAll<T = unknown>(predicates: Predicate<T>[]): Predicate<T> {
  return (value) => predicates.every((predicate) => predicate(value));
}

Refinement is similar to Predicate, but uses TypeScript is type guard.

import { Refinement } from '@bitty/predicate';

const isNumber: Refinement<unknown, number> = (value) =>
  Number.isFinite(value);
//=> Was typed as `(value: unknown) => value is number`.

const value: number | string = Math.random() > 0.5 ? 100 : 'A text.';

if (isNumber(value)) {
  console.log(value.toFixed(2));
  //=> Okay, because type of `value` was refined to `number`.
}
console.log(value.toFixed(2));
//=> Property 'toFixed' does not exist on type 'string | number'.
//     Property 'toFixed' does not exist on type 'string'.

License

Released under MIT License.