57 lines
1.3 KiB
TypeScript
57 lines
1.3 KiB
TypeScript
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import forEach from 'lodash-es/forEach'
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import without from 'lodash-es/without'
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import type {$FixMe} from '../types'
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type Listener = (v: $FixMe) => void
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/**
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* A simple barebones event emitter
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*/
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export default class EventEmitter {
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_listenersByType: {[eventName: string]: Array<Listener>}
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constructor() {
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this._listenersByType = {}
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}
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addEventListener(eventName: string, listener: Listener) {
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const listeners =
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this._listenersByType[eventName] ||
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(this._listenersByType[eventName] = [])
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listeners.push(listener)
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return this
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}
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removeEventListener(eventName: string, listener: Listener) {
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const listeners = this._listenersByType[eventName]
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if (listeners) {
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const newListeners = without(listeners, listener)
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if (newListeners.length === 0) {
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delete this._listenersByType[eventName]
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} else {
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this._listenersByType[eventName] = newListeners
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}
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}
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return this
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}
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emit(eventName: string, payload: unknown) {
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const listeners = this.getListenersFor(eventName)
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if (listeners) {
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forEach(listeners, (listener) => {
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listener(payload)
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})
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}
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}
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getListenersFor(eventName: string) {
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return this._listenersByType[eventName]
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}
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hasListenersFor(eventName: string) {
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return this.getListenersFor(eventName) ? true : false
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}
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}
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