pattern-matching
Syntax-free pattern matching, feature parity with TC39 proposal-pattern-matching.
This project provides syntax-independent, type-safe pattern matching tools.
Table of Contents
Install
deno.land:
import * as mod from "https://deno.land/x/pattern_matching/mod.ts";npm:
npm i @miyauci/pattern-matchingUsage
To start pattern matching, use the match function and the arm function.
arm takes the role of Clause.
The names of the arm function and the proposal clause are as follows:
| Name | Proposal name |
|---|---|
| when | when |
| whether | if |
| otherwise | default |
import {
match,
otherwise,
when,
} from "https://deno.land/x/pattern_matching/mod.ts";
declare const num: number;
const result = match(num)(
when(1, () => "one"),
when(2, () => "two"),
otherwise(() => "many"),
);Binding
Binding binds the value of matchable when matched. This allows subsequent handlers to reference the binding.
import {
_,
match,
otherwise,
when,
whether,
} from "https://deno.land/x/pattern_matching/mod.ts";
import {
assertType,
type IsExact,
} from "https://deno.land/std/testing/types.ts";
interface Person {
name: string;
age: number;
hobby?: string;
greet?: string;
}
declare const person: Person;
const result = match(person)(
whether(({ name, age }) => !name || !age, () => {
throw new Error();
}),
when(
{ greet: _("introduction") },
({ introduction }) => `${introduction}`,
),
when(
{ name: _("name"), hobby: _("hobby") },
({ name, hobby }) => `${name} hobby is ${hobby}`,
),
otherwise(() => "profile does not exist"),
);
assertType<IsExact<typeof result, string>>(true);API
See deno doc for all APIs.
Contributing
See contributing.
License
MIT © 2023 Tomoki Miyauchi