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import {extend} from './util';
type Listener = (Object) => any;
type Listeners = {[_: string]: Array<Listener> };
function _addEventListener(type: string, listener: Listener, listenerList: Listeners) {
const listenerExists = listenerList[type] && listenerList[type].indexOf(listener) !== -1;
if (!listenerExists) {
listenerList[type] = listenerList[type] || [];
listenerList[type].push(listener);
}
}
function _removeEventListener(type: string, listener: Listener, listenerList: Listeners) {
if (listenerList && listenerList[type]) {
const index = listenerList[type].indexOf(listener);
if (index !== -1) {
listenerList[type].splice(index, 1);
}
}
}
export class Event {
+type: string;
constructor(type: string, data: Object = {}) {
extend(this, data);
this.type = type;
}
}
interface ErrorLike {
message: string;
}
export class ErrorEvent extends Event {
error: ErrorLike;
constructor(error: ErrorLike, data: Object = {}) {
super('error', extend({error}, data));
}
}
/**
* Methods mixed in to other classes for event capabilities.
*
* @mixin Evented
*/
export class Evented {
_listeners: Listeners;
_oneTimeListeners: Listeners;
_eventedParent: ?Evented;
_eventedParentData: ?(Object | () => Object);
/**
* Adds a listener to a specified event type.
*
* @param {string} type The event type to add a listen for.
* @param {Function} listener The function to be called when the event is fired.
* The listener function is called with the data object passed to `fire`,
* extended with `target` and `type` properties.
* @returns {Object} `this`
*/
on(type: *, listener: Listener): this {
this._listeners = this._listeners || {};
_addEventListener(type, listener, this._listeners);
return this;
}
/**
* Removes a previously registered event listener.
*
* @param {string} type The event type to remove listeners for.
* @param {Function} listener The listener function to remove.
* @returns {Object} `this`
*/
off(type: *, listener: Listener) {
_removeEventListener(type, listener, this._listeners);
_removeEventListener(type, listener, this._oneTimeListeners);
return this;
}
/**
* Adds a listener that will be called only once to a specified event type.
*
* The listener will be called first time the event fires after the listener is registered.
*
* @param {string} type The event type to listen for.
* @param {Function} listener The function to be called when the event is fired the first time.
* @returns {Object} `this`
*/
once(type: *, listener: Listener) {
this._oneTimeListeners = this._oneTimeListeners || {};
_addEventListener(type, listener, this._oneTimeListeners);
return this;
}
fire(event: Event, properties?: Object) {
// Compatibility with (type: string, properties: Object) signature from previous versions.
// See https://github.com/mapbox/mapbox-gl-js/issues/6522,
// https://github.com/mapbox/mapbox-gl-draw/issues/766
if (typeof event === 'string') {
event = new Event(event, properties || {});
}
const type = event.type;
if (this.listens(type)) {
(event: any).target = this;
// make sure adding or removing listeners inside other listeners won't cause an infinite loop
const listeners = this._listeners && this._listeners[type] ? this._listeners[type].slice() : [];
for (const listener of listeners) {
listener.call(this, event);
}
const oneTimeListeners = this._oneTimeListeners && this._oneTimeListeners[type] ? this._oneTimeListeners[type].slice() : [];
for (const listener of oneTimeListeners) {
_removeEventListener(type, listener, this._oneTimeListeners);
listener.call(this, event);
}
const parent = this._eventedParent;
if (parent) {
extend(
event,
typeof this._eventedParentData === 'function' ? this._eventedParentData() : this._eventedParentData
);
parent.fire(event);
}
// To ensure that no error events are dropped, print them to the
// console if they have no listeners.
} else if (event instanceof ErrorEvent) {
console.error(event.error);
}
return this;
}
/**
* Returns a true if this instance of Evented or any forwardeed instances of Evented have a listener for the specified type.
*
* @param {string} type The event type
* @returns {boolean} `true` if there is at least one registered listener for specified event type, `false` otherwise
* @private
*/
listens(type: string) {
return (
(this._listeners && this._listeners[type] && this._listeners[type].length > 0) ||
(this._oneTimeListeners && this._oneTimeListeners[type] && this._oneTimeListeners[type].length > 0) ||
(this._eventedParent && this._eventedParent.listens(type))
);
}
/**
* Bubble all events fired by this instance of Evented to this parent instance of Evented.
*
* @private
* @returns {Object} `this`
* @private
*/
setEventedParent(parent: ?Evented, data?: Object | () => Object) {
this._eventedParent = parent;
this._eventedParentData = data;
return this;
}
}
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