js-alert/src/event-source.js

A simple JavaScript popup alert manager.

//
// EventSource class - This class provides simple event functionality for classes, with Promise support.
//
//	Usage for once-off event listeners:
//
//		myObj.when("closed").then(function(data) {
//			alert("Closed! " + data);
//		});
//
//
//	Usage for permanent event listeners:
//
//		myObj.on("closed", function(data) {
//			alert("Closed! " + data);
//		});
//
//
//	Usage when triggering an event from a subclass:
//
//		this.emit("closed", "customData");
//


export default class EventSource {
	
	/** Adds an event listener. If callback is null, a Promise will be returned. Note that if using the Promise
	 *  it will only be triggered on the first event emitted. */
	when(eventName, callback = null) {
		
		// Make sure event listener object exists
		this._eventListeners = this._eventListeners || {};
		
		// Make sure event listener array exists
		this._eventListeners[eventName] = this._eventListeners[eventName] || [];
		
		// Check if using promise form
		if (callback) {
			
			// Just add the callback
			this._eventListeners[eventName].push(callback);
			
		} else {
		
			// Return the promise
			return new Promise((onSuccess, onFail) => {
				
				// Promise callbacks can only be used once
				onSuccess._removeAfterCall = true;
				
				// Add success handler to event listener array
				this._eventListeners[eventName].push(onSuccess);
				
			});
		
		}
		
	}
	
	/** Synonyms */
	on() {
		return this.when.apply(this, arguments);
	}
	
	addEventListener() {
		return this.when.apply(this, arguments);
	}
	
	
	
	
	/** Triggers an event. Each argument after the first one will be passed to event listeners */
	emit(eventName, ...args) {
		
		// Get list of callbacks
		var callbacks = this._eventListeners && this._eventListeners[eventName] || [];
		
		// Call events
		for (var callback of callbacks) {
			
			// Call it
			callback.apply(this, args);
			
		}
		
		// Remove callbacks that can only be called once
		for (var i = 0 ; i < callbacks.length ; i++)
			if (callbacks[i]._removeAfterCall)
				callbacks.splice(i--, 1);
		
	}
	
	/** Synonyms */
	trigger() {
		return this.emit.apply(this, arguments);
	}
	
	triggerEvent() {
		return this.emit.apply(this, arguments);
	}
	
}


// Apply as a mixin to a class or object
EventSource.mixin = function(otherClass) {
	
	for (var prop in EventSource.prototype)
		if (EventSource.prototype.hasOwnProperty(prop))
			otherClass[prop] = EventSource.prototype[prop];
	
}