inside_webhook.js

    if (event.message && event.message.text) {
      text = event.message.text
      if (text.toLowerCase().includes('recommend')) { 
        // Generate random user ID
        var userId = uuid();
        // Creates an array of the products from sample products/responses
        var categories = Object.keys(recs.products);
        var randomNumber = Math.floor(Math.random() * categories.length);
        // Select a random category to respond with
        var category = categories[randomNumber];
        // Uses global activate function defined on line 9
        var optimizelyVariation = optimizelyClient.activate('product_recs', userId);
        // Gets response from sample response json given category + variation
        var responseData = recs.products[category][optimizelyVariation];
        var products = responseData.attachment.payload.elements;
        // Adds generated user ID to products for tracking if user clicks to buy
        optimizelyVariation === "single_project" ? helpers.addUserId(userId, products) : helpers.addUserIdSingleProd(userId, products);
        // Sends chatbot response
        sendGenericMessage(sender, responseData);
        continue
    }
    if (event.postback) {
      // Fired when user clicks "Buy Now"  
      var payloadResponse = JSON.parse(event.postback.payload);
      // Grabs userID from payload
      var userId = payloadResponse.user;
      // Builds receipt
      var receipt = helpers.buildReceipt(payloadResponse);
      // Track event to Optimizely
      optlyClient.track('purchased', userId, {}, {revenue:receipt.attachment.payload.summary.total_cost * 100});
      // Send receipt
      sendGenericMessage(sender, receipt);
      continue
    }