A minimal Signal class that lets you connect and disconnect handlers.

Signal.js

/*
 * File: Signal.js
 * Classes: Signal, Signal.Connection
 * Author: Sean Cline
 * Version: .1
 * Description: A minimal Signal class that lets you connect and disconnect handlers to be called when .emit(...) is called.
 * License: You may do whatever you please with this file and any code it contains. It is public domain.
 * Usage:
 *	let sig = new Signal();
 *	let connection1 = sig.connect(function(str) { alert(str + "1") });
 *	let connection2 = sig.connect(function(str) { alert(str + "2") });
 *	
 *	sig.emit("test");
 *	connection2.disconnect();
 *	sig.emit("test");
 *
 *  The above code will alert "test1", "test2", then "test1" again.
 */
"use strict";

class Signal {
	constructor() {
		this.connections_ = [];
	}
	
	emit(...params) {
		for (let connection of this.connections_) {
			connection.call(...params);
		}
	}
	
	emitAsync(...params) {
		let self = this;
		setTimeout(function() {
			self.emit(...params);
		}, 0);
	}
	
	connect(func) {
		let connection = new Signal.Connection(this, func);
		this.connections_.push(connection);
		return connection;
	}
	
	disconnect(connection) {
		let index = this.connections_.indexOf(connection);
		
		if (index > -1) {
			this.connections_.splice(index, 1);
		}
	}
}


Signal.Connection = class {
	constructor(signal, func) {
		this.signal_ = signal;
		this.func_ = func;
	}
	
	disconnect() {
		this.signal_.disconnect(this);
		this.signal_ = this.func_ = undefined;
	}
	
	call(...params) {
		this.func_(...params);
	}
	
	get isConnected() { return typeof(this.func_) != 'undefined'; }
}