main.js

/**
 * DOM event delegator
 *
 * The delegator will listen
 * for events that bubble up
 * to the root node.
 *
 * @constructor
 * @param {Node|string} [root] The root node or a selector string matching the root node
 */
function Delegate(root) {

	/**
	 * Maintain a map of listener
	 * lists, keyed by event name.
	 *
	 * @type Object
	 */
	this.listenerMap = [{}, {}];
	if (root) {
		this.root(root);
	}

	/** @type function() */
	this.handle = Delegate.prototype.handle.bind(this);

	// Cache of event listeners removed during an event cycle
	this._removedListeners = [];
}

/**
 * Start listening for events
 * on the provided DOM element
 *
 * @param  {Node|string} [root] The root node or a selector string matching the root node
 * @returns {Delegate} This method is chainable
 */
Delegate.prototype.root = function (root) {
	const listenerMap = this.listenerMap;
	let eventType;

	// Remove master event listeners
	if (this.rootElement) {
		for (eventType in listenerMap[1]) {
			if (listenerMap[1].hasOwnProperty(eventType)) {
				this.rootElement.removeEventListener(eventType, this.handle, true);
			}
		}
		for (eventType in listenerMap[0]) {
			if (listenerMap[0].hasOwnProperty(eventType)) {
				this.rootElement.removeEventListener(eventType, this.handle, false);
			}
		}
	}

	// If no root or root is not
	// a dom node, then remove internal
	// root reference and exit here
	if (!root || !root.addEventListener) {
		if (this.rootElement) {
			delete this.rootElement;
		}
		return this;
	}

	/**
	 * The root node at which
	 * listeners are attached.
	 *
	 * @type Node
	 */
	this.rootElement = root;

	// Set up master event listeners
	for (eventType in listenerMap[1]) {
		if (listenerMap[1].hasOwnProperty(eventType)) {
			this.rootElement.addEventListener(eventType, this.handle, true);
		}
	}
	for (eventType in listenerMap[0]) {
		if (listenerMap[0].hasOwnProperty(eventType)) {
			this.rootElement.addEventListener(eventType, this.handle, false);
		}
	}

	return this;
};

/**
 * @param {string} eventType
 * @returns boolean
 */
Delegate.prototype.captureForType = function (eventType) {
	return ['blur', 'error', 'focus', 'load', 'resize', 'scroll'].indexOf(eventType) !== -1;
};

/**
 * Attach a handler to one
 * event for all elements
 * that match the selector,
 * now or in the future
 *
 * The handler function receives
 * three arguments: the DOM event
 * object, the node that matched
 * the selector while the event
 * was bubbling and a reference
 * to itself. Within the handler,
 * 'this' is equal to the second
 * argument.
 *
 * The node that actually received
 * the event can be accessed via
 * 'event.target'.
 *
 * @param {string} eventType Listen for these events
 * @param {string|undefined} selector Only handle events on elements matching this selector, if undefined match root element
 * @param {function()} handler Handler function - event data passed here will be in event.data
 * @param {boolean} [useCapture] see 'useCapture' in <https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener>
 * @returns {Delegate} This method is chainable
 */
Delegate.prototype.on = function (eventType, selector, handler, useCapture) {
	let root;
	let listenerMap;
	let matcher;
	let matcherParam;

	if (!eventType) {
		throw new TypeError('Invalid event type: ' + eventType);
	}

	// handler can be passed as
	// the second or third argument
	if (typeof selector === 'function') {
		useCapture = handler;
		handler = selector;
		selector = null;
	}

	// Fallback to sensible defaults
	// if useCapture not set
	if (useCapture === undefined) {
		useCapture = this.captureForType(eventType);
	}

	if (typeof handler !== 'function') {
		throw new TypeError('Handler must be a type of Function');
	}

	root = this.rootElement;
	listenerMap = this.listenerMap[useCapture ? 1 : 0];

	// Add master handler for type if not created yet
	if (!listenerMap[eventType]) {
		if (root) {
			root.addEventListener(eventType, this.handle, useCapture);
		}
		listenerMap[eventType] = [];
	}

	if (!selector) {
		matcherParam = null;

		// COMPLEX - matchesRoot needs to have access to
		// this.rootElement, so bind the function to this.
		matcher = matchesRoot.bind(this);

		// Compile a matcher for the given selector
	} else if (/^[a-z]+$/i.test(selector)) {
		matcherParam = selector;
		matcher = matchesTag;
	} else if (/^#[a-z0-9\-_]+$/i.test(selector)) {
		matcherParam = selector.slice(1);
		matcher = matchesId;
	} else {
		matcherParam = selector;
		matcher = Element.prototype.matches;
	}

	// Add to the list of listeners
	listenerMap[eventType].push({
		selector: selector,
		handler: handler,
		matcher: matcher,
		matcherParam: matcherParam
	});

	return this;
};

/**
 * Remove an event handler
 * for elements that match
 * the selector, forever
 *
 * @param {string} [eventType] Remove handlers for events matching this type, considering the other parameters
 * @param {string} [selector] If this parameter is omitted, only handlers which match the other two will be removed
 * @param {function()} [handler] If this parameter is omitted, only handlers which match the previous two will be removed
 * @returns {Delegate} This method is chainable
 */
Delegate.prototype.off = function (eventType, selector, handler, useCapture) {
	let i;
	let listener;
	let listenerMap;
	let listenerList;
	let singleEventType;

	// Handler can be passed as
	// the second or third argument
	if (typeof selector === 'function') {
		useCapture = handler;
		handler = selector;
		selector = null;
	}

	// If useCapture not set, remove
	// all event listeners
	if (useCapture === undefined) {
		this.off(eventType, selector, handler, true);
		this.off(eventType, selector, handler, false);
		return this;
	}

	listenerMap = this.listenerMap[useCapture ? 1 : 0];
	if (!eventType) {
		for (singleEventType in listenerMap) {
			if (listenerMap.hasOwnProperty(singleEventType)) {
				this.off(singleEventType, selector, handler);
			}
		}

		return this;
	}

	listenerList = listenerMap[eventType];
	if (!listenerList || !listenerList.length) {
		return this;
	}

	// Remove only parameter matches
	// if specified
	for (i = listenerList.length - 1; i >= 0; i--) {
		listener = listenerList[i];

		if ((!selector || selector === listener.selector) && (!handler || handler === listener.handler)) {
			this._removedListeners.push(listener);
			listenerList.splice(i, 1);
		}
	}

	// All listeners removed
	if (!listenerList.length) {
		delete listenerMap[eventType];

		// Remove the main handler
		if (this.rootElement) {
			this.rootElement.removeEventListener(eventType, this.handle, useCapture);
		}
	}

	return this;
};


/**
 * Handle an arbitrary event.
 *
 * @param {Event} event
 */
Delegate.prototype.handle = function (event) {
	let i;
	let l;
	const type = event.type;
	let root;
	let phase;
	let listener;
	let returned;
	let listenerList = [];
	let target;
	const eventIgnore = 'ftLabsDelegateIgnore';

	if (event[eventIgnore] === true) {
		return;
	}

	target = event.target;

	// Hardcode value of Node.TEXT_NODE
	// as not defined in IE8
	if (target.nodeType === 3) {
		target = target.parentNode;
	}

	// Handle SVG <use> elements in IE
	if (target.correspondingUseElement) {
		target = target.correspondingUseElement;
	}

	root = this.rootElement;

	phase = event.eventPhase || (event.target !== event.currentTarget ? 3 : 2);

	// eslint-disable-next-line default-case
	switch (phase) {
		case 1: //Event.CAPTURING_PHASE:
			listenerList = this.listenerMap[1][type];
			break;
		case 2: //Event.AT_TARGET:
			if (this.listenerMap[0] && this.listenerMap[0][type]) {
				listenerList = listenerList.concat(this.listenerMap[0][type]);
			}
			if (this.listenerMap[1] && this.listenerMap[1][type]) {
				listenerList = listenerList.concat(this.listenerMap[1][type]);
			}
			break;
		case 3: //Event.BUBBLING_PHASE:
			listenerList = this.listenerMap[0][type];
			break;
	}

	let toFire = [];

	// Need to continuously check
	// that the specific list is
	// still populated in case one
	// of the callbacks actually
	// causes the list to be destroyed.
	l = listenerList.length;
	while (target && l) {
		for (i = 0; i < l; i++) {
			listener = listenerList[i];

			// Bail from this loop if
			// the length changed and
			// no more listeners are
			// defined between i and l.
			if (!listener) {
				break;
			}

			if (
				target.tagName &&
				["button", "input", "select", "textarea"].indexOf(target.tagName.toLowerCase()) > -1 &&
				target.hasAttribute("disabled")
			) {
				// Remove things that have previously fired
				toFire = [];
			}
			// Check for match and fire
			// the event if there's one
			//
			// TODO:MCG:20120117: Need a way
			// to check if event#stopImmediatePropagation
			// was called. If so, break both loops.
			else if (listener.matcher.call(target, listener.matcherParam, target)) {
				toFire.push([event, target, listener]);
			}
		}

		// TODO:MCG:20120117: Need a way to
		// check if event#stopPropagation
		// was called. If so, break looping
		// through the DOM. Stop if the
		// delegation root has been reached
		if (target === root) {
			break;
		}

		l = listenerList.length;

		// Fall back to parentNode since SVG children have no parentElement in IE
		target = target.parentElement || target.parentNode;

		// Do not traverse up to document root when using parentNode, though
		if (target instanceof HTMLDocument) {
			break;
		}
	}

	let ret;

	for (i = 0; i < toFire.length; i++) {
		// Has it been removed during while the event function was fired
		if (this._removedListeners.indexOf(toFire[i][2]) > -1) {
			continue;
		}
		returned = this.fire.apply(this, toFire[i]);

		// Stop propagation to subsequent
		// callbacks if the callback returned
		// false
		if (returned === false) {
			toFire[i][0][eventIgnore] = true;
			toFire[i][0].preventDefault();
			ret = false;
			break;
		}
	}

	return ret;
};

/**
 * Fire a listener on a target.
 *
 * @param {Event} event
 * @param {Node} target
 * @param {Object} listener
 * @returns {boolean}
 */
Delegate.prototype.fire = function (event, target, listener) {
	return listener.handler.call(target, event, target);
};

/**
 * Check whether an element
 * matches a tag selector.
 *
 * Tags are NOT case-sensitive,
 * except in XML (and XML-based
 * languages such as XHTML).
 *
 * @param {string} tagName The tag name to test against
 * @param {Element} element The element to test with
 * @returns boolean
 */
function matchesTag(tagName, element) {
	return tagName.toLowerCase() === element.tagName.toLowerCase();
}

/**
 * Check whether an element
 * matches the root.
 *
 * @param {?String} selector In this case this is always passed through as null and not used
 * @param {Element} element The element to test with
 * @returns boolean
 */
function matchesRoot(selector, element) {
	if (this.rootElement === window) {
		return (
			// Match the outer document (dispatched from document)
			element === document ||
			// The <html> element (dispatched from document.body or document.documentElement)
			element === document.documentElement ||
			// Or the window itself (dispatched from window)
			element === window
		);
	}
	return this.rootElement === element;
}

/**
 * Check whether the ID of
 * the element in 'this'
 * matches the given ID.
 *
 * IDs are case-sensitive.
 *
 * @param {string} id The ID to test against
 * @param {Element} element The element to test with
 * @returns boolean
 */
function matchesId(id, element) {
	return id === element.id;
}

/**
 * Short hand for off()
 * and root(), ie both
 * with no parameters
 *
 * @return void
 */
Delegate.prototype.destroy = function () {
	this.off();
	this.root();
};

export default Delegate;