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import _ from 'lodash';
export default class EventBus {
constructor() {
this._eventListeners = [];
}
registerListener(event, callback, once=false) {
this._eventListeners = this._eventListeners || [];
this._eventListeners.push({
event: event,
callback: callback,
fired: once ? 'pending' : 'ignore',
});
// helpfull in useEffect where we need to cleanup the listeners.
return ()=>{
this.deregisterListener(event, callback);
};
}
on(...args) {
return this.registerListener(...args);
}
once(...args) {
return this.registerListener(...args, true);
}
deregisterListener(event, callback) {
if(callback) {
this._eventListeners = this._eventListeners.filter((e)=>{
if(e.event === event) {
return e.callback != callback;
}
return true;
});
} else {
this._eventListeners = this._eventListeners.filter((e)=>e.event!=event);
}
}
off(...args) {
this.deregisterListener(...args);
}
fireEvent(event, ...args) {
let self = this;
Promise.resolve(0).then(()=>{
let allListeners = _.filter(this._eventListeners, (e)=>e.event==event);
if(allListeners) {
for(const listener of allListeners) {
Promise.resolve(0).then(()=>{
listener.callback(...args);
if(listener.fired == 'pending') {
self.deregisterListener(event, listener.callback);
}
});
}
}
});
}
trigger(...args) {
this.fireEvent(...args);
}
}