SimpleSubject

Subscribe, notify, unsubscribe

A simple, no-frills subject-observer implementation written in TypeScript.

• Repository
• Implementation
• Examples
• Demo App
• Demo App Repo

Installation

> npm install simple-subject

From source

> git clone [e-mail]:jabney/simple-subject.git
 
> cd simple-subject
 
> npm install
 
> npm run build

Usage

// Import the class
const SimpleSubject = require('simple-subject')
 
// Create an instance
const subject = new SimpleSubject()
 
// Subscribe and define a notification callback
const observer1 = subject.subscribe((payload, id) => {
  console.log(`subscriber ${id}: ${payload}`)
})
 
// Subscribe and define a notification callback
const observer2 = subject.subscribe((payload, id) => {
  console.log(`subscriber ${id}: ${payload}`)
})
 
// Subscribe and define a notification callback
const observer3 = subject.subscribe((payload, id) => {
  console.log(`subscriber ${id}: ${payload}`)
})
 
// Notify all observers
subject.notify({ message: 'notified' })
 
// Unsubscribe observers
for (const observer of [observer1, observer2, observer3]) {
  ovserver.unsubscribe()
}

Output:

subscriber 0: {message: "notified"}
subscriber 1: {message: "notified"}
subscriber 2: {message: "notified"}

Using TypeScript

If your tsconfig.json is set up to use commonjs modules, e.g., "module": "commonjs", you can use require:

import SimpleSubject = require('simple-subject')
 
const subject:SimpleSubject = new SimpleSubject()

However this doesn't work when using ES2015 modules, e.g., "module": "es2015". In this case, use the TypeScript source:

import { SimpleSubject } from 'simple-subject/src'
 
const subject:SimpleSubject = new SimpleSubject()
 

SimpleSubject supports generic notation for specifying the type of the data payload.

import { SimpleSubject, ISubscriptionToken } from 'simple-subject/src'
 
interface IMessage {
  from: string
  with: string
}
 
const doubleOh: SimpleSubject<IMessage> = new SimpleSubject()
 
const mi6:ISubscriptionToken = doubleOh.subscribe((payload, id) => {
  console.log(payload)
})
 
const message:IMessage = { from: 'Russia', with: 'Love' }
 
doubleOh.notify(message)
 
mi6.unsubscribe()

Output:

{ from: "Russia", with: "Love" }