| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | * |
| 7 | * @flow |
| 8 | */ |
| 9 | |
| 10 | import reportGlobalError from 'shared/reportGlobalError'; |
| 11 | |
| 12 | export default class EventEmitter<Events: Object> { |
| 13 | listenersMap: Map<string, Array<Function>> = new Map(); |
| 14 | |
| 15 | addListener<Event: $Keys<Events>>( |
| 16 | event: Event, |
| 17 | listener: (...Events[Event]) => mixed, |
| 18 | ): void { |
| 19 | const listeners = this.listenersMap.get(event); |
| 20 | if (listeners === undefined) { |
| 21 | this.listenersMap.set(event, [listener]); |
| 22 | } else { |
| 23 | const index = listeners.indexOf(listener); |
| 24 | if (index < 0) { |
| 25 | listeners.push(listener); |
| 26 | } |
| 27 | } |
| 28 | } |
| 29 | |
| 30 | emit<Event: $Keys<Events>>(event: Event, ...args: Events[Event]): void { |
| 31 | const listeners = this.listenersMap.get(event); |
| 32 | if (listeners !== undefined) { |
| 33 | if (listeners.length === 1) { |
| 34 | // No need to clone or try/catch |
| 35 | const listener = listeners[0]; |
| 36 | listener.apply(null, args); |
| 37 | } else { |
| 38 | let didThrow = false; |
| 39 | let caughtError = null; |
| 40 | |
| 41 | const clonedListeners = Array.from(listeners); |
| 42 | for (let i = 0; i < clonedListeners.length; i++) { |
| 43 | const listener = clonedListeners[i]; |
| 44 | try { |
| 45 | listener.apply(null, args); |
| 46 | } catch (error) { |
| 47 | if (!didThrow) { |
| 48 | didThrow = true; |
| 49 | caughtError = error; |
| 50 | } else { |
| 51 | // Continue notifying the remaining listeners, but do not hide |
| 52 | // additional failures behind the first one. |
| 53 | reportGlobalError(error); |
| 54 | } |
| 55 | } |
| 56 | } |
| 57 | |
| 58 | if (didThrow) { |
| 59 | throw caughtError; |
| 60 | } |
| 61 | } |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | removeAllListeners(): void { |
| 66 | this.listenersMap.clear(); |
| 67 | } |
| 68 | |
| 69 | removeListener<Event: $Keys<Events>>( |
| 70 | event: Event, |
| 71 | listener: (...Events[Event]) => mixed, |
| 72 | ): void { |
| 73 | const listeners = this.listenersMap.get(event); |
| 74 | if (listeners !== undefined) { |
| 75 | const index = listeners.indexOf(listener); |
| 76 | if (index >= 0) { |
| 77 | listeners.splice(index, 1); |
| 78 | } |
| 79 | } |
| 80 | } |
| 81 | } |