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None = 0,
Capture = 1,
Bubble = 2,
}
type ListenersMap = Map<EventListener, EventListenerPhases>;
/**
* TargetEventListeners adds support for event types with namespace, allow
* removing events without having to pass a callback and makes it possible to
* remove all event listeners in a much simpler way avoiding leaving listeners
* behind which would result in memory leaks.
*
* @example
* Creating a new TargetEventListeners instance
* ```javascript
* const element = document.getElementById('foo');
* const targetEventListeners = new TargetEventListeners(element)
* ```
*
* @example
* Adding and removing event listeners
* ```javascript
* const dragCallback = () => { };
*
* targetEventListeners.addEventListener('voi.mousemove', dragCallback);
* targetEventListeners.addEventListener('voi.drag', dragCallback);
* targetEventListeners.addEventListener('voi.mouseup', () => {
* // do not need to store a reference of this function
* }));
*
* // Removes a specific event listener
* targetEventListeners.removeEventListener('voi.mousemove', dragCallback)
*
* // Removes all "mouseup" event listeners added to "colorbar.voi" namespace
* targetEventListeners.removeEventListener('voi.mouseup')
*
* // Removes all event listeners added to the element using this targetEventListeners
* // instance. A TargetEventListeners instance does not removes the event listeners
* // added by another one.
* targetEventListeners.reset();
* ```
*
* @example
* Adding and removing event listeners for capture and bubble phases. Each
* listener must be removed indenpendently
* ```javascript
* const clickCaptureCallback = () => { };
* const clickBubbleCallback = () => { };
*
* targetEventListeners.addEventListener('click', clickCaptureCallback, { capture: true });
* targetEventListeners.addEventListener('click', clickBubbleCallback);
*
* // Removes the event listener added to the capture phase
* targetEventListeners.removeEventListener('click', clickCaptureCallback, { capture: true });
*
* // Removes the event listener added to the bubble phase
* targetEventListeners.removeEventListener('click', clickBubbleCallback);
*
* // Removes all event listeners added to the HTML element
* targetEventListeners.reset();
* ```
*/
class TargetEventListeners {
private _target: EventTarget;
private _eventListeners = new Map<string, ListenersMap>();
private _children = new Map<string, TargetEventListeners>();
constructor(target: EventTarget) {
this._target = target;
}
public get isEmpty() {
return this._eventListeners.size === 0 && this._children.size === 0;
}
public addEventListener(
type: string,
callback: EventListener,
options?: AddEventListenerOptions
) {
const dotIndex = type.indexOf('.');
const isNamespace = dotIndex !== -1;
if (isNamespace) {
const namespaceToken = type.substring(0, dotIndex);
let childElementEventListener = this._children.get(namespaceToken);
if (!childElementEventListener) {
childElementEventListener = new TargetEventListeners(this._target);
this._children.set(namespaceToken, childElementEventListener);
}
type = type.substring(dotIndex + 1);
childElementEventListener.addEventListener(type, callback, options);
} else {
this._addEventListener(type, callback, options);
}
}
/**
* Remove an event listener with support for namespaces and optional callback
* which makes it remove all listeners of a given type
* @param type - Event type
* @param callback - Event listener
* @param options - Event options
*/
public removeEventListener(
type: string,
callback?: EventListener,
options?: EventListenerOptions
): void {
const dotIndex = type.indexOf('.');
const isNamespace = dotIndex !== -1;
if (isNamespace) {
const namespaceToken = type.substring(0, dotIndex);
const childElementEventListener = this._children.get(namespaceToken);
if (!childElementEventListener) {
return;
}
type = type.substring(dotIndex + 1);
childElementEventListener.removeEventListener(type, callback, options);
// remove empty child objects
if (childElementEventListener.isEmpty) {
this._children.delete(namespaceToken);
}
} else {
this._removeEventListener(type, callback, options);
}
}
/**
* Loop through all types, listeners and phases and removing all of them
*/
public reset() {
// Destroy all children (DFS - depth first search)
Array.from(this._children.entries()).forEach(([namespace, child]) => {
child.reset();
if (child.isEmpty) {
this._children.delete(namespace);
} else {
// This scenario must never happen (safety only)
throw new Error('Child is not empty and cannot be removed');
}
});
this._unregisterAllEvents();
}
private _addEventListener(
type: string,
callback: EventListener,
options?: AddEventListenerOptions
) {
let listenersMap = this._eventListeners.get(type);
if (!listenersMap) {
listenersMap = new Map<EventListener, EventListenerPhases>();
this._eventListeners.set(type, listenersMap);
}
const useCapture = options?.capture ?? false;
const listenerPhase = useCapture
? EventListenerPhases.Capture
: EventListenerPhases.Bubble;
const registeredPhases =
listenersMap.get(callback) ?? EventListenerPhases.None;
// Bitwise operator to see if the current phase is already registered
// because the same listener may be register twice (capturing and bubbling
// phases)
if (registeredPhases & listenerPhase) {
console.warn('A listener is already registered for this phase');
return;
}
// Add a new event listener or updates the existing one for the phase requested
listenersMap.set(callback, registeredPhases | listenerPhase);
// Add the event listener to the target
this._target.addEventListener(type, callback, options);
}
private _removeEventListener(
type: string,
callback?: EventListener,
options?: EventListenerOptions
): void {
const useCapture = options?.capture ?? false;
const listenerPhase = useCapture
? EventListenerPhases.Capture
: EventListenerPhases.Bubble;
const listenersMap = this._eventListeners.get(type);
if (!listenersMap) {
return;
}
// It can remove a single or all callbacks for a given namespace
const callbacks = callback ? [callback] : Array.from(listenersMap.keys());
callbacks.forEach((callbackItem) => {
const registeredPhases =
listenersMap.get(callbackItem) ?? EventListenerPhases.None;
// Bitwise operation to see if the phase is registered
const phaseRegistered = !!(registeredPhases & listenerPhase);
if (!phaseRegistered) {
return;
}
// Remove the event listener from the target
this._target.removeEventListener(type, callbackItem, options);
// Since it is enabled we can XOR it to zero the bit in that position
// 00000011 (capture & buble) ^ 00000010 (buble) = 00000001 (capture)
const newListenerPhase = registeredPhases ^ listenerPhase;
// Deletes the listener if it is no more used in capturing or bubbling
// phases or updates it otherwise
if (newListenerPhase === EventListenerPhases.None) {
listenersMap.delete(callbackItem);
} else {
listenersMap.set(callbackItem, newListenerPhase);
}
});
// Deletes the event from the main map if there are no listeners anymore
if (!listenersMap.size) {
this._eventListeners.delete(type);
}
}
private _unregisterAllListeners(type: string, listenersMap: ListenersMap) {
// Creates a copy with Array.from() because the map mutates every
// time an event listener is removed
Array.from(listenersMap.entries()).forEach(([listener, eventPhases]) => {
const startPhase = EventListenerPhases.Capture;
// currentPhase start at 1 and shifts 1 bit to the left because
// EventListenerPhases is a power of 2
for (let currentPhase = startPhase; eventPhases; currentPhase <<= 1) {
// Check if the current phase is registered
if (!(eventPhases & currentPhase)) {
continue;
}
const useCapture =
currentPhase === EventListenerPhases.Capture ? true : false;
// Remove the event listener for this given phase
this.removeEventListener(type, listener, { capture: useCapture });
// Switch the bit from the "currentPhase" from 1 to 0
eventPhases ^= currentPhase;
}
});
}
private _unregisterAllEvents() {
// Creates a copy with Array.from() because the map mutates every
// time an event listener is removed
Array.from(this._eventListeners.entries()).forEach(([type, listenersMap]) =>
this._unregisterAllListeners(type, listenersMap)
);
}
}
export { TargetEventListeners as default, TargetEventListeners };
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