FAQ

cron.schedule("0 */2 * * *", async () => {
  await checkPrices();
});

• 0 - At minute 0
• */2 - Every 2 hours
• * * * - Every day, month, day of week

• Trigger manual checks using /check command
• The bot checks prices when you first add a product

• 🇺🇸 Amazon.com (United States)
• 🇲🇽 Amazon.com.mx (Mexico)
• 🇬🇧 Amazon.co.uk (United Kingdom)
• 🇩🇪 Amazon.de (Germany)
• 🇫🇷 Amazon.fr (France)
• 🇮🇹 Amazon.it (Italy)
• 🇪🇸 Amazon.es (Spain)
• 🇯🇵 Amazon.co.jp (Japan)
• 🇨🇦 Amazon.ca (Canada)
• 🇦🇺 Amazon.com.au (Australia)
• And any other Amazon regional site

function sanitizeAmazonURL(url) {
  const u = new URL(url);
  return u.origin + u.pathname; // Preserves domain
}

• Currency symbols are preserved from the page
• Product titles appear in the site’s language
• Price parsing removes non-numeric characters (index.mjs:128)

const HISTORY_LIMIT = 120;

1. Recording: Every price check adds a new entry (index.mjs:195)
2. Trimming: If history exceeds 120 entries, oldest entries are removed (index.mjs:196)
3. Storage: History is saved in prices.json with timestamps

• 120 entries × 2 hours = 240 hours
• ≈ 10 days of continuous tracking

{
  "history": [
    { "date": "2026-03-01T10:00:00.000Z", "price": 299.99 },
    { "date": "2026-03-01T12:00:00.000Z", "price": 289.99 },
    { "date": "2026-03-01T14:00:00.000Z", "price": 289.99 }
  ]
}

const selectors = [
  "#productTitle",
  "h1#title",
  "h1.a-size-large",
  'h1[data-automation-id="product-title"]',
  ".product-title"
];

const selectors = [
  "span.a-price .a-offscreen",
  "span#priceblock_ourprice",
  "span#priceblock_dealprice",
  "div#corePrice_feature_div span.a-offscreen"
];

• Modify the CSS selectors in scrapeProduct() function
• Add conditional logic for different domains
• Test thoroughly with the target site

​

Price Storage

• price - Current/most recent price
• lowestPrice - Lowest price ever seen
• history - Array of all price checks

​

Comparison Logic

if (scraped.price < originalPrice) {
  // Price dropped - send notification
}

• Previous price (originalPrice)
• New current price (scraped.price)
• Savings amount (dollar difference)
• Savings percentage
• Historical lowest price

​

Example Scenario

1. Product added: $299.99
   • price = 299.99
   • lowestPrice = 299.99
2. First check (2 hours later): $289.99
   • scraped.price (289.99) < originalPrice (299.99) ✅
   • Notification sent: “¡Precio reducido! $10.00 (3.3% menos)”
   • price = 289.99
   • lowestPrice = 289.99
3. Second check (4 hours later): $289.99
   • scraped.price (289.99) < originalPrice (289.99) ❌
   • No notification (price unchanged)
4. Third check (6 hours later): $309.99
   • scraped.price (309.99) < originalPrice (289.99) ❌
   • No notification (price increased)
   • price = 309.99
   • lowestPrice = 289.99 (unchanged)
5. Fourth check (8 hours later): $279.99
   • scraped.price (279.99) < originalPrice (309.99) ✅
   • Notification sent: “¡Precio reducido! $30.00 (9.7% menos)”
   • Also shows lowest: $279.99

{
  "url": "https://amazon.com/dp/B08N5WRWNW",
  "title": "Product Name",
  "price": 299.99,
  "lowestPrice": 279.99,
  "imageUrl": "https://...",
  "addedDate": "2026-03-01T10:00:00.000Z",
  "addedBy": 123456789,
  "lastChecked": "2026-03-10T14:00:00.000Z",
  "history": [
    { "date": "2026-03-01T10:00:00.000Z", "price": 299.99 }
  ]
}

• url - Sanitized product URL (without query params)
• title - Product name from Amazon
• price - Most recent price
• lowestPrice - Minimum price ever recorded
• imageUrl - Product image for notifications
• addedDate - When you first added the product
• addedBy - Your Telegram chat ID
• lastChecked - Last time price was scraped
• history - Up to 120 price/date pairs

• All data stored locally on your server
• No data sent to external services (except Amazon for scraping)
• Chat IDs stored only for notifications

• Products are stored by URL as the key (index.mjs:21)
• If User A adds a product, User B sees the same product
• All registered chats receive notifications for all products (index.mjs:223)

1. User A adds amazon.com/dp/B08N5WRWNW
2. User B tries to add the same URL
3. Bot responds: ⚠️ Este producto ya está en seguimiento (index.mjs:404-405)

• Price drops notify all registered chats (index.mjs:223-244)
• Chat registration happens automatically on first message (index.mjs:705-712)

• Consider running separate bot instances per user
• Or modify the code to associate products with specific chat IDs

1. Error logged (index.mjs:165-166):
   Error en [Product]: Título no encontrado
   
2. Continues checking other products (index.mjs:170-172)
   • Doesn’t stop entire check process
   • Updates lastChecked timestamp
   • Moves to next product
3. Retries on next scheduled check (2 hours later)

• Delays between requests: 800-900ms (index.mjs:78, 214)
• Headless browser: Appears more like real user
• Reasonable check frequency: Every 2 hours, not aggressive
• Browser flags: --no-sandbox for compatibility (index.mjs:148)

• Multiple consecutive scraping failures
• “Título no encontrado” errors
• “Precio inválido” errors
• Captcha pages (not handled by bot)

1. Wait several hours before retrying
2. Reduce check frequency (modify cron at index.mjs:733)
3. Track fewer products simultaneously
4. Use residential proxy (requires code modification)

• Tracking current deal prices
• Detecting when deal price drops further
• Recording deal price in history

1. Product normally $100
2. Lightning deal: $60 (you add it)
3. Bot tracks at $60
4. Deal expires, price returns to $100
5. Bot sees $100 >$60, no notification sent
6. Bot continues tracking at $100

"span#priceblock_dealprice",  // Catches deal prices
"span#priceblock_ourprice",   // Regular price
"span.a-price .a-offscreen"   // General price

• Add products before deals start for better tracking
• Use /chart to see when deal occurred in history
• Manually remove products after deals expire if desired

1. Copy the data file:
   cp prices.json my-backup-$(date +%Y%m%d).json
   
2. Convert to CSV (using jq):
   jq -r '.products | to_entries[] | [.key, .value.title, .value.price, .value.lowestPrice, .value.lastChecked] | @csv' prices.json > prices.csv
   
3. Extract history for specific product:
   jq '.products["YOUR_URL"].history' prices.json > product-history.json
   

let priceData = {};  // keys: sanitizedUrl -> product object
let chats = new Set();

{
  "products": { /* url -> product */ },
  "chats": [ /* array of chat IDs */ ]
}

​

/list Command (index.mjs:489)

• Shows interactive menu of all products
• Click products to see details
• Buttons to delete all or check prices
• Best for: Managing your products

​

/stats Command (index.mjs:492-517)

• Shows aggregate statistics:
  • Total products tracked
  • Total chats registered
  • Potential savings detected
  • Products with price reductions
• Best for: Overview of activity

📊 Estadísticas de seguimiento

📦 Productos: 5
👥 Chats registrados: 2
💰 Ahorro potencial detectado: $45.32
📉 Productos con precio reducido: 3

/edit [current_url] [new_url]

/edit https://amazon.com/dp/OLD123 https://amazon.com/dp/NEW456

1. Bot scrapes the new URL
2. Transfers existing history
3. Preserves addedDate and addedBy
4. Keeps lowestPrice from both old and new
5. Deletes old URL entry
6. Creates new URL entry

• Product URL changed (Amazon redirects)
• Wrong product added by mistake
• Variant changed (different size/color)

/chart [product_url]

• At least 2 history entries (minimum 4 hours of tracking)
• Valid product URL that you’re tracking

• X-axis: Timestamps (date/time)
• Y-axis: Price values
• Line graph showing price changes over time
• Product title as chart title

• Generated using Chart.js (index.mjs:268)
• Rendered via Playwright browser screenshot (index.mjs:253-307)
• Image size: 900×420 pixels (index.mjs:266)
• Sent as photo to Telegram

📊 Histórico de precios
[Chart image showing price drops over time]
Product Name
[Ver en Amazon] button