o-pubsub

Object matching publish/subscribe pattern

Why bother defining routes and topics when you can subscribe to data?

Easy to use pubsub mechanism using objects instead of strings

as a standalone

const PubSub=require('o-pubsub').standalone;// import a standalone pub sub
const {publish,subscribe} = PubSub();//create a pubsub module

const unsubscribe=subscribe({hello:'there'},(data)=> console.log(data));//will log {hello:'there',meaning:{of:{life:42}}} only once
publish({hello:'there',meaning:{of:{life:42}}});
publish({hello:'you',meaning:{of:{life:42}}});
unsubscribe();
publish({hello:'there',meaning:{of:{life:42}}});

or as a web service

const OPubSub = require('o-pubsub');
const PubSubServer =OPubSub.restServer();//import the server without options
const PubSub=OPubsub.restClient;// import a pub sub Client

const next=()=>{
  const {publish,subscribe} = PubSub();//create a pubsub module without parameters gives an example one
  const unsubscribe=subscribe({hello:'there'},(data)=> console.log(data));//will log {hello:'there',meaning:{of:{life:42}}} only once
  publish({hello:'there',meaning:{of:{life:42}}});
  publish({hello:'you',meaning:{of:{life:42}}});
  unsubscribe();
  publish({hello:'there',meaning:{of:{life:42}}});
}

const server = PubSubServer.listen(3000,next);

wildcards '*' and wild path '**' are implemented on subscriptions

const testWildPath=()=>{
  const pubSub = require('o-pubsub').standalone();
    let results = [];
    const msg = { '*': {floor2:{floor3:'hello'}} };
    const msg2 = { floor1: {'*':{floor3:'hello'}} };
    const msg3 = { '*': {floor2:{'*':'hello'}} };
    const msg4 = { '*': {'*':{'*':'hello'}} };
    const errmsg = {'*':'hello'};
    pubSub.subscribe(msg, data => {
      results.push(data);
    });
    pubSub.subscribe(msg2, data => {
      results.push(data);
    });
    pubSub.subscribe(msg3, data => {
      results.push(data);
    });
    pubSub.subscribe(msg4, data => {
      results.push(data);
    });
    pubSub.subscribe(errmsg, data => {
      results.push(data);
    });
    pubSub.publish({floor1:{floor2:{floor3:'hello'}}});

    setTimeout(() => {
      console.log(results);// [{floor1:{floor2:{floor3:'hello'}}},{floor1:{floor2:{floor3:'hello'}}},{floor1:{floor2:{floor3:'hello'}}},{floor1:{floor2:{floor3:'hello'}}}];
    }, 10);
}

const testwildpath=()=>{
    const pubSub = require('o-pubsub').standalone();
    const msg = { '**':'hello'};
    const errMsg = { '**':'NOPE'};
    pubSub.subscribe(msg, console.log); //{floor1:{floor2:{floor3:'hello'}}}
    pubSub.subscribe(errMsg, data => {
      throw new Error('Should not be invoked');
    });
    
    pubSub.publish({floor1:{floor2:{floor3:'hello'}}});
}

Constructors

|Name|Comment|Options| | ------------- | ------------- | ------------- | |standalone({options})| returns publish and subscribe methods| options:{ matcher:(candidate,pattern)=>return boolean}| |restServer({options})| returns Express.js server| options:{ matcher:(candidate,pattern)=>return boolean}| |restClient({options}) |returns publish and subscribe methods, options are http requests one.| default{ hostname: 'localhost', port: 3000, path: '/o-pubsub/', method: 'GET', headers: { 'Content-Type': 'application/json' }}|

Create your own matcher and pass it as a parameters, candidate and pattern can be anything.

Methods

|Name | Comment| | ------------- | ------------- | |publish(data)| send data to every pattern subscribers.| |unsubscribe=subscribe(pattern,callback)| subscribe to the pattern, return the unsubscribe method. as it's a FireAndForget, ensure to store this method.| |unsubscribe()|unsubscribe to pattern.|

API

restClient is a wrapper for restServer but you could implement it on your own:

| Name | Comment | | --------------------------- | ------------- | | get('/o-pubsub/') | returns 'o-pubsub is online'.| | post('/o-pubsub/') | will publish req.body.| | put('/o-pubsub/:id') | will subscribe to req.body, ensure to store id for unsubscription.| | delete('/o-pubsub/:id') | unsubscribe to pattern registered with given id.|

publish and subscribe accept Object,number,regexp,string,Array note: on array the comparison is made first on type then on length, not on data inside.