Event not emitting inside derived class of event emitter in Node Js - node.js

Question

tinyscrapper.js
I am emitting scrapeStarted event in scrap function
const EventEmitter = require("events");
const axios = require("axios");
const cheerio = require("cheerio");
const { exit } = require("process");
class TinyScraper extends EventEmitter {
constructor(url, timeout) {
super();
this.scrap(url,timeout) }
async scrap(url, timeout) {
this.emit("scrapeStarted");
let results=null;
try {
setTimeout(
() => {
console.log("timeout");
if (!results) {
this.emit("timeout");
exit(1)
}
},
timeout
);
const { data } = await axios.get(url);
// Load HTML we fetched in the previous line
const $ = cheerio.load(data);
const title = $('meta[property="og:title"]').attr("content");
const image = $('meta[property="og:image"]').attr("content");
const desc = $('meta[property="og:description"]').attr("content");
results={ title: title,
image: `strong text`image,
description:desc}
this.emit("scrapeSuccess", results);
} catch (err) {
this.emit("error", err);
}
}
}
module.exports = TinyScraper;
I am listening scrapeStarted event in index.js but the event does not listen while it is called in TinyScrapper class. An exciting thing is an error, timeout and scrapeSuccess event is working fine
Index.js
// index.js
const TinyScraper = require('./tiny-scraper');
const scraper = new TinyScraper('http://localhost:8000/url1',20000);
scraper.on('scrapeSuccess', (data) => {
console.log('JSON Data received scrapping:', data);
});
scraper.on('scrapeStarted', (data) => {
console.log('Started Scraping:', data);
});
scraper.on('error', () => {
console.log('The URL is not valid.');
});
scraper.on('timeout', () => {
console.log('Scraping timed out');
});

Answer 1

Your scraper starts scraping before you've registered event listeners. You'll need to register event listeners and then call scrap yourself.
class TinyScraper extends EventEmitter {
constructor(url, timeout) {
this.url = url;
this.timeout = timeout
super();
}
async scrape() {
const {url, timeout} = this;
this.emit("scrapeStarted");
// ... rest of method
}
}
And then your index.js needs to be refactored to
const TinyScraper = require('./tiny-scraper');
const scraper = new TinyScraper('http://localhost:8000/url1',20000);
scraper.on('scrapeSuccess', (data) => {
console.log('JSON Data received scrapping:', data);
});
// other .on handlers
scraper.scrape();