The JavaScript Automations That Turned My Side Projects Into Passive Income Machines

1. The Day I Realized JavaScript Could Be My Cash Cow I always thought of JavaScript as just the thing that makes websites interactive. But then I built my first browser automation that collected market data for me, and it hit me — this wasn’t just code, it was a money-making engine. The key was finding repeatable tasks that people would pay to have done faster and turning them into automated JS scripts.

2. Puppeteer — My Secret Weapon for Browser Automation Puppeteer lets you control Chrome programmatically. Imagine clicking, typing, and scraping data like a human — but 1,000 times faster.

const puppeteer = require('puppeteer');

(async () => {
    const browser = await puppeteer.launch({ headless: true });
    const page = await browser.newPage();

    await page.goto('https://example.com/products');
    const products = await page.evaluate(() => {
        return [...document.querySelectorAll('.product')].map(item => ({
            name: item.querySelector('.title').innerText,
            price: item.querySelector('.price').innerText
        }));
    });

    console.log(products);
    await browser.close();
})();

I used this for price monitoring scripts that I sold to small e-commerce stores.

3. Node.js + Cheerio — Web Scraping Without the Browser Sometimes you don’t need a full browser; you just need the HTML. That’s where Cheerio comes in.

const axios = require('axios');
const cheerio = require('cheerio');

(async () => {
    const { data } = await axios.get('https://example.com/blog');
    const $ = cheerio.load(data);
    
    const posts = [];
    $('.post-title').each((i, el) => {
        posts.push($(el).text());
    });
    
    console.log(posts);
})();

I used this for content aggregation sites that pulled trending blog posts and made ad revenue.

4. Express.js — Turning Scripts Into Web Services Once you’ve automated something, why not turn it into an API and sell access?

const express = require('express');
const app = express();
const port = 3000;

app.get('/prices', async (req, res) => {
    // Imagine this calls Puppeteer and returns fresh data
    res.json({ item: 'Laptop', price: '$799' });
});

app.listen(port, () => console.log(`Server running on http://localhost:${port}`));

I sold API subscriptions to businesses that needed real-time pricing data.

5. Playwright — The New Kid That’s Even Better Than Puppeteer Playwright can automate multiple browsers (Chromium, Firefox, WebKit) and is perfect for projects where clients want cross-browser testing.

6. Building Chrome Extensions That Sell Extensions can be mini SaaS businesses. I built a LinkedIn Auto-Connect tool and charged users $5/month.

chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
    if (msg.action === 'connect') {
        document.querySelectorAll('.connect-button').forEach(btn => btn.click());
        sendResponse({ status: 'done' });
    }
});

7. Using Stripe.js for Payments If you’re selling scripts or API access, you’ll need payments. Stripe.js makes it easy.

8. Automating Social Media With Node.js Automated posting to Twitter/X, Instagram, and LinkedIn with APIs. Perfect for social media managers who want to scale.

9. Combining APIs for Arbitrage Opportunities Example: Pull hotel prices from one API, compare them to another, and sell the cheaper booking.

10. Packaging & Selling Scripts on Gumroad Once you’ve built a tool, package it, write clear docs, and sell it as a downloadable product.

Read the full article here: https://javascript.plainenglish.io/the-javascript-automations-that-turned-my-side-projects-into-passive-income-machines-be25a740b195