Edit: Added errorEvent option to configure error events
99% of my event adaptation of promises end up looking something close to this:
function open(file) {
return new Promise((resolve, reject) => {
const stream = fs.createWriteStream(file)
function ready() {
stream.removeListener("ready", ready)
stream.removeListener("error", fail)
resolve(stream)
}
function fail(e) {
reject(e)
stream.removeListener("ready", ready)
stream.removeListener("error", fail)
}
stream.on("ready", ready)
stream.on("error", fail)
})
}This is most frequently with streams, but it also occasionally shows up with other things, including with non-core libraries. What I'd prefer to write is something closer to this:
async function open(file) {
const stream = fs.createWriteStream(file)
await stream.awaitEvent("ready")
return stream
}My proposed API is this:
ee.awaitEvent("name", {includeAll = false, errorEvent = "event"} = {}): Return a promise fulfilled with an array of arguments once "name" is emitted, rejected if it's beat by an "error" event. An extra options object is permitted, and it accepts two options: includeAll, which resolves with an array of arguments intead, and errorEvent, which allows configuring what event is considered the "error" event.
The naïve implementation is pretty simple, and looks very similar to above.
EventEmitter.prototype.awaitEvent = function awaitEvent(event, {includeAll, errorEvent = "event"} = {}) {
return new Promise((resolve, reject) => {
const success = (...args) => {
this.removeListener(event, success)
this.removeListener(errorEvent, fail)
if (includeAll) resolve(...args)
else resolve(args[0])
}
const fail = e => {
reject(e)
this.removeListener(event, success)
this.removeListener(errorEvent, fail)
}
this.on(event, success)
this.on(errorEvent, fail)
})
}
Edit: Added
errorEventoption to configure error events99% of my event adaptation of promises end up looking something close to this:
This is most frequently with streams, but it also occasionally shows up with other things, including with non-core libraries. What I'd prefer to write is something closer to this:
My proposed API is this:
ee.awaitEvent("name", {includeAll = false, errorEvent = "event"} = {}): Return a promise fulfilled with an array of arguments once"name"is emitted, rejected if it's beat by an"error"event. An extra options object is permitted, and it accepts two options:includeAll, which resolves with an array of arguments intead, anderrorEvent, which allows configuring what event is considered the "error" event.The naïve implementation is pretty simple, and looks very similar to above.