Amazon Price Difference Highlighter Chrome extension

// manifest.json
{
  "manifest_version": 3,
  "name": "Amazon Price Difference Highlighter",
  "version": "1.0",
  "description": "Highlights items with significant price differences in Amazon cart",
  "permissions": ["activeTab"],
  "content_scripts": [
    {
      "matches": [
            "*://*.amazon.com/*",
            "*://*.amazon.co.uk/*",
            "*://*.amazon.de/*",
            "*://*.amazon.fr/*",
            "*://*.amazon.nl/*",
            "*://*.amazon.com.be/*"
         ],
    }
  ],
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  }
}

// content.js
function extractPrice(priceText) {
    // Extract numerical value from price string (assumes € format)
    return parseFloat(priceText.replace('€', '').trim());
}

function addStarToTitle(titleElement) {
    const star = document.createElement('span');
    star.innerHTML = '⭐ ';
    star.style.color = '#f4c542';
    titleElement.insertBefore(star, titleElement.firstChild);
}

function analyzePriceDifferences() {
    // Select all price change messages
    const priceChangeItems = document.querySelectorAll('li span.a-list-item span[data-feature-id="single-imb-message"]');
    
    priceChangeItems.forEach(item => {
        // Find price elements
        const prices = item.querySelectorAll('.sc-product-price');
        if (prices.length === 2) {
            const oldPrice = extractPrice(prices[0].textContent);
            const newPrice = extractPrice(prices[1].textContent);
            
            // Calculate price difference
            const priceDifference = Math.abs(oldPrice - newPrice);
            
            // If difference is more than 10 euros, add star
            if (priceDifference > 10) {
                const titleElement = item.querySelector('.sc-product-title');
                if (titleElement && !titleElement.querySelector('span')) {
                    addStarToTitle(titleElement);
                }
            }
        }
    });
}

// Run the analysis when the page loads
analyzePriceDifferences();

// Optional: Run periodically to catch dynamic updates
setInterval(analyzePriceDifferences, 5000);

a Chrome extension that analyzes price differences and adds star icons where appropriate, in this case where the price difference is 10 euro. Change that amount at will on line 53.

Take this gist and split it up in two files, a manifest file and a content script that runs on Amazon's cart page.

Add some basic icons (icon48.png and icon128.png) to the directory
Load the extension in Chrome:

Go to chrome://extensions/
Enable "Developer mode" (top right)
Click "Load unpacked"
Select your extension directory