@zwyssigly/functional v0.0.4

Introduction

Functional is a package to improve your code stability and make your code more explicit, by adopting two common monads Option and Result from functional languages like Rust.

Installation

npm install @zwyssigly/functional --save

How to use Result

// import stuff
import { Result, Ok, Err } from '@zwyssigly/functional'

// function returning Result
function parseDate(value: string | undefined) : Result<Date, string>{
	if (!value)
		return Err('Can not convert falsable to a date')

	let number = Date.parse(value);
	if (isNan(number))
		return Err('Can not parse string as date')
	
	return Ok(new Date(number));
}

// async function returning Result
async function saveDate(value: Date) : Promise<Result<Date, string> {
	// your persistance logic
	return Ok(value);
}

// putting it together in an express endpoint
app.post('/api/date', async (req, res) => {
	await parseDate(req.body.date)
		.andThenAsync(date => saveDate(date))
		.match<void>(ok => res.send(ok), err => res.status(400).send(err));
});

How to use Option

// import stuff
import { Some, None, Option } from '@zwyssigly/funtional`

// returning option
function getDate(id: string) : Option<Date>
{
	if (exists(id))
		return Some(new Date());
	return None;
}

let option = getDate('today');

// execute something if none
option.ifNone(() => console.log("No date with such id));

// map some value
let stringOption: Option<string> = option.map(some => some.toString());

// execute match option
let dateAsString = option.match(some => some.toString(), () => 'None');