emit

Synchronously trigger the specified event.

Method Signature

Provides a total of 8 overload signatures, where T is the event type, Events is the events object, and Meta is the metadata object.

Type-safe Basic Usage

This form can infer the event type from the event generic parameters provided when constructing FastEvent.

//
emit<R = any, T extends Types = Types>(
    type: T,
    payload?: Events[T],
    options?: FastEventListenerArgs<Meta>
): R[]
// Specify retain
emit<R = any, T extends Types = Types>(
    type: T,
    payload?: Events[T],
    retain?: boolean
): R[]

• Example

import { FastEvent } from 'fastevent';

const emitter = new FastEvent<{
    click: number;
    focus: string;
    blur: boolean;
}>();

emitter.emit('
click', 100);
//
//
//
//

String Event Type

Directly specify any string event type.

emit<R = any, T extends string = string>(
    type: T,
    payload?: T extends Types ? Events[Types] : any,
    retain?: boolean
): R[]
emit<R = any, T extends string = string>(
    type: T,
    payload?: T extends Types ? Events[Types] : any,
    options?: FastEventListenerArgs<Meta>
): R[]

Type-safe Message Object Parameter

emit<R = any, T extends string = string>(
    message: FastEventEmitMessage<{ [K in T]: K extends Types ? Events[K] : any }, Meta>,
    retain?: boolean
): R[]
emit<R = any, T extends string = string>(
    message: FastEventEmitMessage<{ [K in T]: K extends Types ? Events[K] : any }, Meta>,
    options?: FastEventListenerArgs<Meta>
): R[]

Message Object Parameter

emit<R = any>(
    message: FastEventEmitMessage<Events, Meta>,
    retain?: boolean
): R[]
emit<R = any>(
    message: FastEventEmitMessage<Events, Meta>,
    options?: FastEventListenerArgs<Meta>
): R[]

Parameters

Parameter	Type	Description
type	T	The event type to trigger; can be automatically inferred
payload	Events[T]	Event payload data
options	FastEventListenerArgs	Whether to retain the event data
options.retain	boolean	Whether to retain the message; if true, the last message is retained. See Retain Messages
options.meta	Record<string, any>	Event metadata, passed to the listeners
options.abortSignal	AbortSignal	Passed to the listener function. See Abort Listeners
options.executor	FastListenerExecutorArgs	Controls listener execution behavior. See Executors

Return Value

The emit function returns the return values of all matching listener functions.

const emitter = new FastEvent<{ click: number }>();

emit.on('click', () => 1)
emit.on('click', () => {throw new Error('custom'))
emit.on('click', async () =>2 )
emit.on('click', async () => {throw new Error('custom'))

const results = emit('click', 100);
// [1,Error,Promise,Promise]

• You can specify a generic parameter R to indicate the return type of the listener functions; R[] is the return type of the listener functions, defaulting to any[].