117 lines
3.6 KiB
TypeScript
117 lines
3.6 KiB
TypeScript
export type EventType = string | symbol;
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// An event handler can take an optional event argument
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// and should not return a value
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export type Handler<T = unknown> = (event: T) => void;
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export type WildcardHandler<T = Record<string, unknown>> = (
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type: keyof T,
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event: T[keyof T]
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) => void;
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// An array of all currently registered event handlers for a type
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export type EventHandlerList<T = unknown> = Array<Handler<T>>;
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export type WildCardEventHandlerList<T = Record<string, unknown>> = Array<WildcardHandler<T>>;
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// A map of event types and their corresponding event handlers.
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export type EventHandlerMap<Events extends Record<EventType, unknown>> = Map<
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keyof Events | '*',
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EventHandlerList<Events[keyof Events]> | WildCardEventHandlerList<Events>
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>;
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type GenericEventHandler<Events extends Record<EventType, unknown>> =
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| Handler<Events[keyof Events]>
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| WildcardHandler<Events>;
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export class Emitter<Events extends Record<EventType, unknown>> {
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/**
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* A Map of event names to registered handler functions.
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*/
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public all: EventHandlerMap<Events>;
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public constructor() {
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this.all = new Map();
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}
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public resetAll() {
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this.all = new Map();
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}
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public reset<Key extends keyof Events>(type: Key) {
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this.all!.set(type, [] as EventHandlerList<Events[keyof Events]>);
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}
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on<Key extends keyof Events>(type: Key, handler: Handler<Events[Key]>): void;
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on(type: '*', handler: WildcardHandler<Events>): void;
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/**
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* Register an event handler for the given type.
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* @param {string|symbol} type Type of event to listen for, or `'*'` for all events
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* @param {Function} handler Function to call in response to given event
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* @memberOf mitt
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*/
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public on<Key extends keyof Events>(type: Key, handler: GenericEventHandler<Events>) {
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const handlers: Array<GenericEventHandler<Events>> | undefined = this.all!.get(type);
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if (handlers) {
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handlers.push(handler);
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}
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else {
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this.all!.set(type, [handler] as EventHandlerList<Events[keyof Events]>);
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}
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}
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off<Key extends keyof Events>(type: Key, handler?: Handler<Events[Key]>): void;
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off(type: '*', handler: WildcardHandler<Events>): void;
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/**
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* Remove an event handler for the given type.
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* If `handler` is omitted, all handlers of the given type are removed.
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* @param {string|symbol} type Type of event to unregister `handler` from, or `'*'`
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* @param {Function} [handler] Handler function to remove
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* @memberOf mitt
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*/
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public off<Key extends keyof Events>(type: Key, handler?: GenericEventHandler<Events>) {
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const handlers: Array<GenericEventHandler<Events>> | undefined = this.all!.get(type);
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if (handlers) {
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if (handler) {
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handlers.splice(handlers.indexOf(handler) >>> 0, 1);
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}
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else {
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this.all!.set(type, []);
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}
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}
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}
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emit<Key extends keyof Events>(type: Key, event: Events[Key]): void;
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emit<Key extends keyof Events>(type: undefined extends Events[Key] ? Key : never): void;
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/**
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* Invoke all handlers for the given type.
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* If present, `'*'` handlers are invoked after type-matched handlers.
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*
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* Note: Manually firing '*' handlers is not supported.
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*
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* @param {string|symbol} type The event type to invoke
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* @param {Any} [evt] Any value (object is recommended and powerful), passed to each handler
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* @memberOf mitt
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*/
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emit<Key extends keyof Events>(type: Key, evt?: Events[Key]) {
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let handlers = this.all!.get(type);
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if (handlers) {
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(handlers as EventHandlerList<Events[keyof Events]>)
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.slice()
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.map((handler) => {
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handler(evt!);
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});
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}
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handlers = this.all!.get('*');
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if (handlers) {
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(handlers as WildCardEventHandlerList<Events>)
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.slice()
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.map((handler) => {
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handler(type, evt!);
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});
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}
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}
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} |