mirror of
https://github.com/puppeteer/puppeteer
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86 lines
2.6 KiB
TypeScript
86 lines
2.6 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 = any> = (event?: T) => void;
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export type WildcardHandler = (type: EventType, event?: any) => void;
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// An array of all currently registered event handlers for a type
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export type EventHandlerList = Array<Handler>;
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export type WildCardEventHandlerList = Array<WildcardHandler>;
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// A map of event types and their corresponding event handlers.
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export type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;
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export interface Emitter {
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all: EventHandlerMap;
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on<T = any>(type: EventType, handler: Handler<T>): void;
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on(type: '*', handler: WildcardHandler): void;
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off<T = any>(type: EventType, handler: Handler<T>): void;
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off(type: '*', handler: WildcardHandler): void;
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emit<T = any>(type: EventType, event?: T): void;
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emit(type: '*', event?: any): void;
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}
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/**
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* Mitt: Tiny (~200b) functional event emitter / pubsub.
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* @name mitt
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* @returns {Mitt}
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*/
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export default function mitt(all?: EventHandlerMap): Emitter {
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all = all || new Map();
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return {
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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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all,
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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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on<T = any>(type: EventType, handler: Handler<T>) {
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const handlers = all.get(type);
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const added = handlers && handlers.push(handler);
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if (!added) {
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all.set(type, [handler]);
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}
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},
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/**
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* Remove an event handler for the given type.
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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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off<T = any>(type: EventType, handler: Handler<T>) {
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const handlers = all.get(type);
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if (handlers) {
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handlers.splice(handlers.indexOf(handler) >>> 0, 1);
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}
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},
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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<T = any>(type: EventType, evt: T) {
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((all.get(type) || []) as EventHandlerList).slice().map((handler) => { handler(evt); });
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((all.get('*') || []) as WildCardEventHandlerList).slice().map((handler) => { handler(type, evt); });
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}
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};
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}
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