How do I JSDoc custom EventEmitter on events in Visual Studio Code? - node.js

Question

I've been working on a Node.js project and only just noticed that Visual Studio Code provides information about base EventEmitter objects. So I imagine it should be possible to provide JSDoc for custom ones too.
I've already attempted following the JSDoc http://usejsdoc.org/tags-event.html documentation but doesn't seem to pick up.
I don't know if this is effecting it but I'm using the ES6 class where the events get processed in a function outside it but it's inside the same script.
This is the test code.
// voice
if (voice) {
try {
/**
* Voice event.
*
* #event TelegramBot#voice
* #type {object}
* #property {object} chat - [object Chat]
* #property {number} date - Date when content was sent.
* #property {object} from - [object User]
* #property {number} message_id - Message id.
* #property {string} caption - Caption added to message. Value is undefined if none is added.
* #property {object} voice - [object Voice]
*/
context.emit('voice', chat, date, from, message_id, caption, voice)
} catch (error) {
context.emit('error', error)
}
}

Answer 1

I found this question while attempting to do the same, so I kept searching and I found a possible solution, by overriding the addListener methods, and documenting them.
I successfully made it work for both NodeJS and browser JS.
Result in VSCode
Typedef
First, create the typedef with your events names :
/**
* #typedef {["someEvent" | "someOtherEvent", ...any[]]} eventsDef
*/
I am using the spread syntax since I don't know how many arguments the user will pass to the method.
Implementation
For NodeJS:
The class needs to override the on and addListener methods, document the arguments, and simply call the parent's own method :
class Test extends EventEmitter {
/**
* #param {eventsDef} args
*/
addListener(...args) {
super.addListener(...args);
}
/**
* #param {eventsDef} args
*/
on(...args) {
super.on(...args);
}
fireEvent() {
this.emit("someEvent", "someValue");
}
}
Then you can use this class like so :
const t = new Test();
t.on("someEvent", (val) => console.log(val));
t.fireEvent(); // Outputs "someValue"
For the browser:
The class needs to extends EventTarget and override the addEventListener method.
Here is the snippet :
class Test extends EventTarget {
/**
* #param {["someEvent" | "someOtherEvent", ...any[]]} args
*/
addEventListener(...args) {
super.addEventListener(...args);
}
fireEvent() {
this.dispatchEvent(new CustomEvent("someEvent", {detail: "someValue"}))
}
}
const t = new Test();
t.addEventListener("someEvent", val => console.log(val.detail));
document.querySelector("button").addEventListener("click", () => {
t.fireEvent();
})
<button>Fire event</button>