About

Simple library inspired by pattern matching in functional languages like F# and others. Of cause it's not so powerful however it simplify some scenarios and as pattern matching can either return a new value or simply control execution flow.

Installation

Simply run

npm install --save alta-match

Examples

Let's solve a classical issue called FizzBuzz

import {Match} from 'alta-match';

const  fizzBuzzMatch  =  Match.create<number, string>()
	.with(x => x % 5 === 0 && x % 3 === 0, _ => 'Fizz Buzz')
	.with(x => x % 3 === 0, _ => 'Fizz')
	.with(x => x % 5 === 0, _ => 'Buzz')
	.with(_ => true, x  =>  x.toString());

for(let i = 1; i < 100; i++) {
	console.log(fizzBuzzMatch.execute(i));
}

We define here matching rules and what to do in each case. It's how we can simply match something and then map it to something else. Actually when we created a match object we defined the input and output types. In this case input is a number and output is a string. We also can use it just to control execution flow, in this case we don't need an output type, we can't omit it, but we can use type void. Here is an example:

import {Match} from 'alta-match';

Match.create<number, void>()
    .with(x => x < 42, _ => console.log('It\'s a small number'))
    .with(x => x > 42, _ => console.log('It\'s too big'))
    .with(x => x < 42, _ => console.log('Magic number !!!'))
    .execute(73);

We do not return anything here, just execute different code.