Using match

iron-oxide offers a rudimentary way to mimic rust's match keyword. In rust the match keyword is used similarly to the way a switch statement is used in JavaScript and TypeScript, except for one key difference: match works with more than just primitive values.

API

match takes two arguments

• The value, of type T, we are matching
• A list of MatchStatements, which are generic over T the type of the value, and R the return value of the match

Each match statement is a tuple of two things

• The value, of type T, or a predicate function which takes the value and returns a boolean
• The function to call if the predicate matches. This receives the matched value

If no statement is matched, and matchUtils.fallback is not given, match will throw an error.

Example

With a primitive value

import { match } from 'iron-oxide';

function getParity(n: number) {
    return match(n, [
        [0, () => 'neitherEvenNorOdd'],
        [x => x % 2 === 0, () => 'even'],
        [x => x % 2 !== 0. () => 'odd']
    ]);
}

With an Option (here, find returns Option<Person>)

import { match } from 'iron-oxide`;

function getPerson(name: string) {
    const maybePerson = find(people, person => person.name === name);

    return match(maybePerson, [
        [isNone, () => console.log("Couldn't find a person with the name:", name)],
        [isSome, (person) => console.log("Found the person:", person)]
    ]);
}

matchUtils

iron-oxide also exports a set of utilities that can be used with a matchStatement, these are

• isOption, matches any Option
• isSome, matches any Some
• isNone, matches any None
• isResult, matches any Result
• isOk, matches any Ok
• isErr, matches any Err
• fallthrough, which matches any and all values