Abort Execution

FastEvent provides a solution to abort the execution of asynchronous listeners by passing an AbortSignal to all event listeners during emit.

Basic Usage

import { FastEvent } from "fastevent"

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

emitter.on("click",  (message,{abortSignal}) => {
    await new Promise((resolve) => { 
        abortSignal.addEventListener("abort", ()=>{
            clearTimeout(tmId)
            resolve()
        })
        doSomething()
        resolve()
    })
})

// Create an AbortController instance
const abortController = new AbortController()

// Pass AbortController.signal
emitter.emit("click", 1,{
    signal: abortController.signal
})
//
abortController.abort()   

• Create an AbortController instance and pass its AbortController.signal when calling emit.
• In the asynchronous listener, use abortSignal to listen for the abort event.

Guide

Passing an Already Aborted Signal

If an already aborted AbortSignal is passed during emit, the listener will directly return an AbortError.

import { FastEvent } from "fastevent"

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

emitter.on("click",  (message,{abortSignal}) => {
    
})

// Create an AbortController instance
const abortController = new AbortController()

abortController.abort()   


// Pass AbortController.signal
const results = emitter.emit("click", 1,{
    signal: abortController.signal
})
//
console.log(results)   // [AbortError]

Handling Abort Signal

In asynchronous listeners, use abortSignal to listen for the abort event.

When the abort event is triggered, the listener can choose to either return normally or throw an AbortError.

import { FastEvent } from "fastevent"

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

emitter.on("click",  (message,{abortSignal}) => {
    return new Promise<void>((resolve, reject) => {        
        abortSignal.addEventListener("abort", ()=>{
            clearTimeout(tmId)
            reject(new AbortError())
        })
        doSomething()
        resolve()
    })
})

// Create an AbortController instance
const abortController = new AbortController()

// Pass AbortController.signal
const results = emitter.emit("click", 1,{
    signal: abortController.signal
})
//
console.log(results)   // [Promise]

setTimeout(()=>{
    abortController.abort()   
},3000)