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3.5 kBTypeScriptView Raw
1/**
2 * Minimal `EventEmitter` interface that is molded against the Node.js
3 * `EventEmitter` interface.
4 */
5declare class EventEmitter<
6 EventTypes extends EventEmitter.ValidEventTypes = string | symbol,
7 Context extends any = any
8> {
9 static prefixed: string | boolean;
10
11 /**
12 * Return an array listing the events for which the emitter has registered
13 * listeners.
14 */
15 eventNames(): Array<EventEmitter.EventNames<EventTypes>>;
16
17 /**
18 * Return the listeners registered for a given event.
19 */
20 listeners<T extends EventEmitter.EventNames<EventTypes>>(
21 event: T
22 ): Array<EventEmitter.EventListener<EventTypes, T>>;
23
24 /**
25 * Return the number of listeners listening to a given event.
26 */
27 listenerCount(event: EventEmitter.EventNames<EventTypes>): number;
28
29 /**
30 * Calls each of the listeners registered for a given event.
31 */
32 emit<T extends EventEmitter.EventNames<EventTypes>>(
33 event: T,
34 ...args: EventEmitter.EventArgs<EventTypes, T>
35 ): boolean;
36
37 /**
38 * Add a listener for a given event.
39 */
40 on<T extends EventEmitter.EventNames<EventTypes>>(
41 event: T,
42 fn: EventEmitter.EventListener<EventTypes, T>,
43 context?: Context
44 ): this;
45 addListener<T extends EventEmitter.EventNames<EventTypes>>(
46 event: T,
47 fn: EventEmitter.EventListener<EventTypes, T>,
48 context?: Context
49 ): this;
50
51 /**
52 * Add a one-time listener for a given event.
53 */
54 once<T extends EventEmitter.EventNames<EventTypes>>(
55 event: T,
56 fn: EventEmitter.EventListener<EventTypes, T>,
57 context?: Context
58 ): this;
59
60 /**
61 * Remove the listeners of a given event.
62 */
63 removeListener<T extends EventEmitter.EventNames<EventTypes>>(
64 event: T,
65 fn?: EventEmitter.EventListener<EventTypes, T>,
66 context?: Context,
67 once?: boolean
68 ): this;
69 off<T extends EventEmitter.EventNames<EventTypes>>(
70 event: T,
71 fn?: EventEmitter.EventListener<EventTypes, T>,
72 context?: Context,
73 once?: boolean
74 ): this;
75
76 /**
77 * Remove all listeners, or those of the specified event.
78 */
79 removeAllListeners(event?: EventEmitter.EventNames<EventTypes>): this;
80}
81
82declare namespace EventEmitter {
83 export interface ListenerFn<Args extends any[] = any[]> {
84 (...args: Args): void;
85 }
86
87 export interface EventEmitterStatic {
88 new <
89 EventTypes extends ValidEventTypes = string | symbol,
90 Context = any
91 >(): EventEmitter<EventTypes, Context>;
92 }
93
94 /**
95 * `object` should be in either of the following forms:
96 * ```
97 * interface EventTypes {
98 * 'event-with-parameters': any[]
99 * 'event-with-example-handler': (...args: any[]) => void
100 * }
101 * ```
102 */
103 export type ValidEventTypes = string | symbol | object;
104
105 export type EventNames<T extends ValidEventTypes> = T extends string | symbol
106 ? T
107 : keyof T;
108
109 export type ArgumentMap<T extends object> = {
110 [K in keyof T]: T[K] extends (...args: any[]) => void
111 ? Parameters<T[K]>
112 : T[K] extends any[]
113 ? T[K]
114 : any[];
115 };
116
117 export type EventListener<
118 T extends ValidEventTypes,
119 K extends EventNames<T>
120 > = T extends string | symbol
121 ? (...args: any[]) => void
122 : (
123 ...args: ArgumentMap<Exclude<T, string | symbol>>[Extract<K, keyof T>]
124 ) => void;
125
126 export type EventArgs<
127 T extends ValidEventTypes,
128 K extends EventNames<T>
129 > = Parameters<EventListener<T, K>>;
130
131 export const EventEmitter: EventEmitterStatic;
132}
133
134export { EventEmitter }
135export default EventEmitter;