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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
const log = LogManager.getLogger("event-emitter");
export var EventEmitter = function () {
const listeners = {};
return {
emit(eventName, event) {
// Fire events async
Promise.resolve().then(() => {
if (!(eventName in listeners)) {
log.debug(
`EventEmitter: Event fired with no listeners: ${eventName}`
);
return;
}
// Clone callbacks array to avoid problems with mutation while iterating
const callbacks = Array.from(listeners[eventName]);
for (const cb of callbacks) {
// Clone event so it can't by modified by the handler
let eventToPass = event;
if (typeof event === "object") {
eventToPass = Object.assign({}, event);
}
cb(eventToPass);
}
});
},
on(eventName, callback) {
if (!(eventName in listeners)) {
listeners[eventName] = [];
}
listeners[eventName].push(callback);
},
off(eventName, callback) {
if (eventName in listeners) {
const index = listeners[eventName].indexOf(callback);
if (index !== -1) {
listeners[eventName].splice(index, 1);
}
}
},
once(eventName, callback) {
const inner = event => {
callback(event);
this.off(eventName, inner);
};
this.on(eventName, inner);
},
};
};