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TypeScript

/**
Emittery accepts strings and symbols as event names.
Symbol event names can be used to avoid name collisions when your classes are extended, especially for internal events.
*/
type EventName = string | symbol;
/**
Emittery also accepts an array of strings and symbols as event names.
*/
type EventNames = EventName | readonly EventName[];
declare class Emittery {
/**
In TypeScript, it returns a decorator which mixins `Emittery` as property `emitteryPropertyName` and `methodNames`, or all `Emittery` methods if `methodNames` is not defined, into the target class.
@example
```
import Emittery = require('emittery');
@Emittery.mixin('emittery')
class MyClass {}
const instance = new MyClass();
instance.emit('event');
```
*/
static mixin(emitteryPropertyName: string | symbol, methodNames?: readonly string[]): Function;
/**
Fires when an event listener was added.
An object with `listener` and `eventName` (if `on` or `off` was used) is provided as event data.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
emitter.on(Emittery.listenerAdded, ({listener, eventName}) => {
console.log(listener);
//=> data => {}
console.log(eventName);
//=> '🦄'
});
emitter.on('🦄', data => {
// Handle data
});
```
*/
static readonly listenerAdded: unique symbol;
/**
Fires when an event listener was removed.
An object with `listener` and `eventName` (if `on` or `off` was used) is provided as event data.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
const off = emitter.on('🦄', data => {
// Handle data
});
emitter.on(Emittery.listenerRemoved, ({listener, eventName}) => {
console.log(listener);
//=> data => {}
console.log(eventName);
//=> '🦄'
});
off();
```
*/
static readonly listenerRemoved: unique symbol;
/**
Subscribe to one or more events.
Using the same listener multiple times for the same event will result in only one method call per emitted event.
@returns An unsubscribe method.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
emitter.on('🦄', data => {
console.log(data);
});
emitter.on(['🦄', '🐶'], data => {
console.log(data);
});
emitter.emit('🦄', '🌈'); // log => '🌈' x2
emitter.emit('🐶', '🍖'); // log => '🍖'
```
*/
on(eventName: typeof Emittery.listenerAdded | typeof Emittery.listenerRemoved, listener: (eventData: Emittery.ListenerChangedData) => void): Emittery.UnsubscribeFn
on(eventName: EventNames, listener: (eventData?: unknown) => void): Emittery.UnsubscribeFn;
/**
Get an async iterator which buffers data each time an event is emitted.
Call `return()` on the iterator to remove the subscription.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
const iterator = emitter.events('🦄');
emitter.emit('🦄', '🌈1'); // Buffered
emitter.emit('🦄', '🌈2'); // Buffered
iterator
.next()
.then(({value, done}) => {
// done === false
// value === '🌈1'
return iterator.next();
})
.then(({value, done}) => {
// done === false
// value === '🌈2'
// Revoke subscription
return iterator.return();
})
.then(({done}) => {
// done === true
});
```
In practice you would usually consume the events using the [for await](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of) statement. In that case, to revoke the subscription simply break the loop.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
const iterator = emitter.events('🦄');
emitter.emit('🦄', '🌈1'); // Buffered
emitter.emit('🦄', '🌈2'); // Buffered
// In an async context.
for await (const data of iterator) {
if (data === '🌈2') {
break; // Revoke the subscription when we see the value `🌈2`.
}
}
```
It accepts multiple event names.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
const iterator = emitter.events(['🦄', '🦊']);
emitter.emit('🦄', '🌈1'); // Buffered
emitter.emit('🦊', '🌈2'); // Buffered
iterator
.next()
.then(({value, done}) => {
// done === false
// value === '🌈1'
return iterator.next();
})
.then(({value, done}) => {
// done === false
// value === '🌈2'
// Revoke subscription
return iterator.return();
})
.then(({done}) => {
// done === true
});
```
*/
events(eventName: EventNames): AsyncIterableIterator<unknown>
/**
Remove one or more event subscriptions.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
const listener = data => console.log(data);
(async () => {
emitter.on(['🦄', '🐶', '🦊'], listener);
await emitter.emit('🦄', 'a');
await emitter.emit('🐶', 'b');
await emitter.emit('🦊', 'c');
emitter.off('🦄', listener);
emitter.off(['🐶', '🦊'], listener);
await emitter.emit('🦄', 'a'); // nothing happens
await emitter.emit('🐶', 'b'); // nothing happens
await emitter.emit('🦊', 'c'); // nothing happens
})();
```
*/
off(eventName: EventNames, listener: (eventData?: unknown) => void): void;
/**
Subscribe to one or more events only once. It will be unsubscribed after the first
event.
@returns The event data when `eventName` is emitted.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
emitter.once('🦄').then(data => {
console.log(data);
//=> '🌈'
});
emitter.once(['🦄', '🐶']).then(data => {
console.log(data);
});
emitter.emit('🦄', '🌈'); // Logs `🌈` twice
emitter.emit('🐶', '🍖'); // Nothing happens
```
*/
once(eventName: typeof Emittery.listenerAdded | typeof Emittery.listenerRemoved): Promise<Emittery.ListenerChangedData>
once(eventName: EventNames): Promise<unknown>;
/**
Trigger an event asynchronously, optionally with some data. Listeners are called in the order they were added, but executed concurrently.
@returns A promise that resolves when all the event listeners are done. *Done* meaning executed if synchronous or resolved when an async/promise-returning function. You usually wouldn't want to wait for this, but you could for example catch possible errors. If any of the listeners throw/reject, the returned promise will be rejected with the error, but the other listeners will not be affected.
*/
emit(eventName: EventName, eventData?: unknown): Promise<void>;
/**
Same as `emit()`, but it waits for each listener to resolve before triggering the next one. This can be useful if your events depend on each other. Although ideally they should not. Prefer `emit()` whenever possible.
If any of the listeners throw/reject, the returned promise will be rejected with the error and the remaining listeners will *not* be called.
@returns A promise that resolves when all the event listeners are done.
*/
emitSerial(eventName: EventName, eventData?: unknown): Promise<void>;
/**
Subscribe to be notified about any event.
@returns A method to unsubscribe.
*/
onAny(listener: (eventName: EventName, eventData?: unknown) => unknown): Emittery.UnsubscribeFn;
/**
Get an async iterator which buffers a tuple of an event name and data each time an event is emitted.
Call `return()` on the iterator to remove the subscription.
In the same way as for `events`, you can subscribe by using the `for await` statement.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery();
const iterator = emitter.anyEvent();
emitter.emit('🦄', '🌈1'); // Buffered
emitter.emit('🌟', '🌈2'); // Buffered
iterator.next()
.then(({value, done}) => {
// done is false
// value is ['🦄', '🌈1']
return iterator.next();
})
.then(({value, done}) => {
// done is false
// value is ['🌟', '🌈2']
// revoke subscription
return iterator.return();
})
.then(({done}) => {
// done is true
});
```
*/
anyEvent(): AsyncIterableIterator<unknown>
/**
Remove an `onAny` subscription.
*/
offAny(listener: (eventName: EventName, eventData?: unknown) => void): void;
/**
Clear all event listeners on the instance.
If `eventName` is given, only the listeners for that event are cleared.
*/
clearListeners(eventName?: EventNames): void;
/**
The number of listeners for the `eventName` or all events if not specified.
*/
listenerCount(eventName?: EventNames): number;
/**
Bind the given `methodNames`, or all `Emittery` methods if `methodNames` is not defined, into the `target` object.
@example
```
import Emittery = require('emittery');
const object = {};
new Emittery().bindMethods(object);
object.emit('event');
```
*/
bindMethods(target: object, methodNames?: readonly string[]): void;
}
declare namespace Emittery {
/**
Removes an event subscription.
*/
type UnsubscribeFn = () => void;
type EventNameFromDataMap<EventDataMap> = Extract<keyof EventDataMap, EventName>;
/**
Maps event names to their emitted data type.
*/
interface Events {
// Blocked by https://github.com/microsoft/TypeScript/issues/1863, should be
// `[eventName: EventName]: unknown;`
}
/**
The data provided as `eventData` when listening for `Emittery.listenerAdded` or `Emittery.listenerRemoved`.
*/
interface ListenerChangedData {
/**
The listener that was added or removed.
*/
listener: (eventData?: unknown) => void;
/**
The name of the event that was added or removed if `.on()` or `.off()` was used, or `undefined` if `.onAny()` or `.offAny()` was used.
*/
eventName?: EventName;
}
/**
Async event emitter.
You must list supported events and the data type they emit, if any.
@example
```
import Emittery = require('emittery');
const emitter = new Emittery.Typed<{value: string}, 'open' | 'close'>();
emitter.emit('open');
emitter.emit('value', 'foo\n');
emitter.emit('value', 1); // TS compilation error
emitter.emit('end'); // TS compilation error
```
*/
class Typed<EventDataMap extends Events, EmptyEvents extends EventName = never> extends Emittery {
on<Name extends EventNameFromDataMap<EventDataMap>>(eventName: Name, listener: (eventData: EventDataMap[Name]) => void): Emittery.UnsubscribeFn;
on<Name extends EmptyEvents>(eventName: Name, listener: () => void): Emittery.UnsubscribeFn;
events<Name extends EventNameFromDataMap<EventDataMap>>(eventName: Name): AsyncIterableIterator<EventDataMap[Name]>;
once<Name extends EventNameFromDataMap<EventDataMap>>(eventName: Name): Promise<EventDataMap[Name]>;
once<Name extends EmptyEvents>(eventName: Name): Promise<void>;
off<Name extends EventNameFromDataMap<EventDataMap>>(eventName: Name, listener: (eventData: EventDataMap[Name]) => void): void;
off<Name extends EmptyEvents>(eventName: Name, listener: () => void): void;
onAny(listener: (eventName: EventNameFromDataMap<EventDataMap> | EmptyEvents, eventData?: EventDataMap[EventNameFromDataMap<EventDataMap>]) => void): Emittery.UnsubscribeFn;
anyEvent(): AsyncIterableIterator<[EventNameFromDataMap<EventDataMap>, EventDataMap[EventNameFromDataMap<EventDataMap>]]>;
offAny(listener: (eventName: EventNameFromDataMap<EventDataMap> | EmptyEvents, eventData?: EventDataMap[EventNameFromDataMap<EventDataMap>]) => void): void;
emit<Name extends EventNameFromDataMap<EventDataMap>>(eventName: Name, eventData: EventDataMap[Name]): Promise<void>;
emit<Name extends EmptyEvents>(eventName: Name): Promise<void>;
emitSerial<Name extends EventNameFromDataMap<EventDataMap>>(eventName: Name, eventData: EventDataMap[Name]): Promise<void>;
emitSerial<Name extends EmptyEvents>(eventName: Name): Promise<void>;
}
}
export = Emittery;