Simple Signal

This is a super-simple signals class inspired by Robert Penner's AS3Signals.

Signals are like Events, Delegates, or Callbacks on other languages or platforms. You can create a signal that other parts of the code can "listen" to. When that signal is dispatched, all listeners are called with the passed parameters.

SimpleSignal is created with TypeScript, but aimed to be used as a standard JavaScript library.

Install

1npm install simplesignal

Usage

First, import your signal:

1// Import (JavaScript ES5)
2var SimpleSignal = require('simplesignal');
3
4// Import (JavaScript ES6 and TypeScript)
5import SimpleSignal from 'simplesignal';

Then, you can create a signal. For example, inside a class:

1public onSomethingHappened = new SimpleSignal();

Then other parts of the code can subscribe (listen) to that signal:

1myClassObject.onSomethingHappened.add((id) => {
2    console.log("Something happened with an id of " + id);
3});

Signals can then be dispatched with parameters:

1onSomethingHappened.dispatch("some-id");

This will call all subscribed functions with the given parameter.

Full reference (JS)

1// Create
2onSomethingHappened = new SimpleSignal();
3
4// Subscribe
5onSomethingHappened.add(myFunc);
6
7// Anonymous functions are, of course, fine
8onSomethingHappened.add(function() { ... });
9onSomethingHappened.add(() => { ... });
10
11// Unsubscribe
12onSomethingHappened.remove(myFunc);
13
14// Clear subscribers
15onSomethingHappened.removeAll();
16
17// Number of subscribers
18console.log(onSomethingHappened.numItems);
19
20// Dispatch
21onSomethingHappened.dispatch(...args)

Additional TypeScript reference

If your project already uses TypeScript, it has the advantage of using SimpleSignal's definition files for strict typing.

In this case, one can use a generic interface to enforce the correct dispatch/listener parameters:

1// Create, with a given interface as a Generic
2onSomethingHappened = new SimpleSignal<(action:string) => void>();
3
4// The listeners must fulfill the interface
5function myFunc(action:string) {
6    console.log(action);
7}
8
9// Subscribe
10onSomethingHappened.add(myFunc);
11
12// Dispatch must also respect the interface
13onSomethingHappened.dispatch("some-action")

License

MIT.