Crummm-emitter-system NPM

Crummm Emitter System

A zero-dependency emitter system with some fancy features under the hood.

Just tell me how to install it!

$ npm i crummm-emitter-system --save

Great...what's it for?

The original intent of this system was to decouple components, libraries, services, etc by allowing them to communicate anonymously. That said, there's countless ways to use emitter systems.

Aren't there like a million emit/on, pub/sub, event/listener systems out there already?

You betcha, and somehow none of them did the trick for me. My dev soul was deeply saddened by the following:

wonky implementation
unfulfilling feature-sets
framework dependencies
a lack of TypeScript support
developers who fell asleep at the wheel (that's my job!)

Plus, I wanted some advanced features like those referenced later in this documentation.

All that said, will this system work for you? Probably not. Ha! But I kind of like it, so there is that.

Fancy words aside, let's get to the meat and potatoes of this thing.

Basic features

emit and listen by type
remove listeners by
- type and callback
- all by type
- all
do once listeners

Advanced features

listen order: this is cool as hell and quite necessary when specific execution order is required
requests: anonymously emit a request and listen for a anonymous response...super simple...super cool
two different ways to use
- create any number of system instances: new CrummmEmitterSystemInstance()
- single system instance via static class methods: CrummmEmitterSystem

Enough talk! What's the implementation look like?!

I hear you! I hate when I have to dig through source code just to get a sense of what the implementation looks like. Fear not, I'll hold your hand through this.

Request example

// listen for requests
CrummmEmitterSystem.onRequest(
  "helloRequest",
  (responseCallback: Function, requestValue: any)=> {
    responseCallback("Hello " + requestValue + "!");
  }
);

// make request for data
CrummmEmitterSystem.emitRequest(
  "helloRequest",
  (response: string)=> {
    console.log(response);
  },
  "Billy"
);

// output: 
// Hello Billy!

Listen order example

const TYPE = "TYPE";
const emitter = new CrummmEmitterSystemInstance();

emitter.onOnce(
  TYPE,
  (payload) => {
    console.log("This should fire 3rd even though it's setup 1st: ", payload.message);
  },
  5 // this param is the listen order!
);

emitter.onOnce(
  TYPE,
  (payload) => {
    console.log("This should fire 1st even though it's setup 2nd: ", payload.message);
  },
  1 // so is this! notice it's a lower number than the previous 'onOnce' listener...so it'll fire before it.
);

emitter.onOnce(
  TYPE,
  (payload) => {
    console.log("This should fire 2nd even though it's setup 3rd: ", payload.message);
  },
  2 // someone has to be in the middle of this sandwich...and since 2 is in-between 1 and 5 it looks like we found our victim.
);

setTimeout(
  () => {
    emitter.emit(TYPE, { message: "Hello listenOrder!" });
  },
  1000
);

// console.log:
// This should fire 1st even though it's setup 2nd:  Hello listenOrder!
// This should fire 2nd even though it's setup 3rd:  Hello listenOrder!
// This should fire 3rd even though it's setup 1st:  Hello listenOrder!

How to go forward...

TODO - npm

Install / setup / npm

$ npm -i

Run

$ npm start

Test

$ npm test

Examples

Check out the 'examples' directory for different implementations and usages.

Errors

What'd you do wrong now?! Hey, don't beat yourself up, I've probably done the same thing already. Check out my mistakes and (hopefully) solutions below!

tsc command not found
- when: occurs after attempting to run command $ npm start
- mistake: something got jacked up...so I'm not beating myself up for this one
- solution: $ npm install typescript -g