Web scraping with Deno

Finding a house is hard. Finding your home is harder.

So during this holidays, I though that I should build a scraper to gather data from real estate websites.

This seems be an overkill solution, but the initial aim is to practice with Deno and MongoDB. Plus, I read many other articles where other tried and found it useful, so maybe will be for me.

Gathering data is only a part of the game, I know, but for now let me focus on that.

My approach was to elude bot-blocking policies with least effort, but without flood the website with requests.

For example I added some work, like traversing html and saving on database, or a waiting time after each request.

Deno doesn’t have a proper sleep function and setTimeout doesn’t work asyncronusly, so here the method i found to sleep asyncronously (and randomly).

const delay = Math.ceil(Math.rand() * 5000); // random milliseconds - max 5 seconds
await new Promise((r) => setTimeout(r, delay)); // the waiting promise.

To elude bot-blocking policies, I ended up to buy a vpn plan subcription. But maybe it didn’t worth it. Let me explain.

In italy we have some websites with real estate ads, I started with what I think were the main one: immobiliare.it and CENSORED.

To do HTML traversing and gather data, I used cheerio a jquery-like library for node and Deno.

Immobiliare.it were a peace of cake, await fetch('immobiliare.it/whatever') does not trigger anything. In the single ad page there was a json object with all the data of the house.

On the other hand on CENSORED after few requests 403 Forbidden errors where given.

What does it mean do request with fetch only? For any webserver the request is clearly from automation:

So I needed a headless browser. A proper browser without interface.

Puppeteer is library to run headless Chrome or Firefox and is ported in Deno by Luca Casonato. So with this lib I can address this problems one by one.

The easy-one was to run the js and wait that the document end loading.

const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://*CENSORED*/whatever', {
  waitUntil: 'domcontentloaded',

In many articles with best practice to scraping they say: rotate useragent. After some research I’ve found this API that gave a json with the percentage of useragent used in the world. So randomly I select a user agent from those that shoud pass always the faking user agent test

After that nothing seems working with CENSORED, it always gave me 403 response. So I thought that my IP was compromised.

At that point I’ve come to conclusion that I need some proxies and a VPN cames along: I choosed Mullvad VPN, 5€/month and come with a CLI useful for automation, not a sponsor.

After a while, I ended up on the CENSORED website with my regular browser and after asking me to solve a captcha it got me in to the website freely. From the scraper it continued to give me 403.

So let’s copy all the cookies!. After copy all the non-session cookies from my browser, even disconnected from VPN, the scraper works.

Thank you Immobiliare.it, because you made my life easer the first time I tried to scrape. Thank you CENSORED, because you gave me some interesting challenge and dig deeper in the scraping world. Anyhow I had to remove the name of the second website because have explicit in his term of service to exclude scraping, anyhow thank you for not sue me…for now.