Algebraify
Algebraic Effects Are Here! (sort of)
(If you’re unfamiliar with algebraic effects, here’s a great article: Algebraic Effects for the Rest of Us)
This is a single-goal library that utilizes generators to add algebraic effects to javascript and typescript.
Usage
Add it to your project by using npm install algebraify or yarn add algebraify, in case you didn’t know.
Examples
Javascript
sync:
import algebra from "algebraify";
const getUser = algebra(function* getUser(_, id) {
const name = getNameOfUser(id) ?? (yield "name");
const age = getAgeOfUser(id) ?? (yield "age");
return `USER ${name}: ${age} years old`;
});
const userString = getUser(100)
.case("name", "John Smith")
.case("age", 18)
.do();
// userString will fallback to using the name john smith and the age 18 if those respective calls fail
async:
// Just change to an async generator function
const getUser = algebra(async function* getUser(_, id) {
const name = await getNameOfUser(id) ?? (yield "name");
const age = await getAgeOfUser(id) ?? (yield "age");
return `USER ${name}: ${age} years old`;
});
// And then await the promise returned by do()
const userString = await getUser(100)
.case("name", "John Smith")
.case("age", 18)
.do();
Typescript
import algebra from "algebraify";
const getUser = algebra(function* getUser(request, id: number) {
// Note the calls to request and subsequent calls to as
const name = getNameOfUser(id) ?? (yield* request("name").as<string>());
const age = getAgeOfUser(id) ?? (yield* request("age").as<number>());
return `USER ${name}: ${age} years old`;
});
const userString = getUser(100)
.case("name", "John Smith")
.case("age", 18)
.do();
// userString will have the type `USER: ${string}: ${number} years old`
// Async changes are identical in ts
The request parameter is a function that returns a narrowly typed iterator. You don’t need to know the details of how it works to use it; yield* request("name").as<string>() is basically the same as doing yield "name", but using some type magic to tell typescript to trust us on the return type.
Contributing
Please contribute! I’ve never made a library that I wanted other people to use before, and my experience with JS/TS is small compared to my programming career. I’d appreciate it a ton!
