dgelong
v0.0.20
Published
A JavaScript Implementation of Useful First-class Citizens
Downloads
6
Maintainers
Readme
Dgelong
It's not ready for production. Stay tuned.
Set of useful first-class structures which allow you to get rid of your developer's pain.
- Flatten by default.
- Minimal API sufrace area.
- Immutable.
- Lazy evaluation.
- Full interoperability between all structures and JavaScript natives.
Install
npm install dgelong --save
Motivation
I've read Fantasy Land specification. I don't want make another implementation that requires Ph.D in Math. The usage of monads should be as simple as functional composition f(g(a))
. API should be close to native. So if we're talking about data structures, they should be produced in the same way as natives: by calling constructor function with or without new
operator (I prefer the second approach).
Usage
Note: Babel is used for transpiling Dgelong's sources. The author highly recommends you to start using ECMAScript 6 in your project.
Dgelong's bundle uses UMD so it can be required in all environments (CommonJS, AMD, ES6 modules, browser).
CommonJS
var Dgelong = require('dgelong');
ECMAScript 6
Just like in CommonJS Modules style you can grab everything in one object:
import Dgelong from 'dgelong';
Or just use something specific, for example:
import {Maybe, Future} from 'dgelong';
But, along with that, you can import particular structures by using direct paths:
import Maybe, {Just, Nothing} from 'dgelong/maybe';
import Either, {Right, Left} from 'dgelong/either';
import Future, {Resolve, Reject} from 'dgelong/future';
import Observable from 'dgelong/observable';
Browser
<script src="node_modules/dgelong/bundle.js"></script>
It will provide you Dgelong
global variable.
Time & Space
- Time (
bind
,subscribe
)- Future (async task as value)
- Observable (async lists)
- Space (
bind
,pull
)- Maybe (null-safe computations)
- Either (two-way composition)
Maybe
import {Just, Nothing} from 'dgelong/maybe';
function square(n) {
return n * n;
}
function isEven(n) {
return n % 2 ? Nothing() : Just(n);
}
Just(5)
.bind(square) // returns Just(25)
.bind(isEven) // returns Nothing()
.bind(alert); // won't work
Either
import {Right as Success, Left as Failure} from 'dgelong/either';
function validateUserPassword(password) {
if (password.length < 10) return Failure('Password too short');
if (!/[0-9]/g.test(password)) return Failure('Password should contain numbers');
return Success(password);
}
validateUserPassword('boo')
.bind(savePassword, showError);
Future
import Future from 'dgelong/future';
function fetch(url) {
return Future(function(resolve, reject) {
var xhr = new XMLHttpRequest();
xhr.onload = () => resolve(this.response);
xhr.onerror = () => reject(this);
xhr.open(url);
xhr.send(null);
return {
dispose() { xhr.abort(); }
};
});
}
fetch('/products')
.bind(products => ...)
.subscribe(showProducts);
Observable
import Observable from 'dgelong/observable';
var clicks = Observable(function(next){
document.addEventListener('click', next);
return {
dispose(){ document.removeEventListener('click', next); }
};
});
clicks
.map(event => event.target)
.forEach(element => ...);