DOCSP-32718: aggregation code comments (#764)

* DOCSP-32718: aggregation code comments

* fixes

Author: rustagir

source/code-snippets/aggregation/agg.js

@@ -1,4 +1,7 @@
+// Perform an aggregation
+
 const { MongoClient } = require("mongodb");
+
 const uri = process.env.MONGDODB_URI;
 const client = new MongoClient(uri);
 
@@ -7,6 +10,7 @@ async function run() {
     const db = client.db("aggregation");
     const coll = db.collection("restaurants");
 
+    // Create sample documents
     const docs = [
         { stars: 3, categories: ["Bakery", "Sandwiches"], name: "Rising Sun Bakery" },
         { stars: 4, categories: ["Bakery", "Cafe", "Bar"], name: "Cafe au Late" },
@@ -15,19 +19,25 @@ async function run() {
         { stars: 4, categories: ["Bakery", "Dessert"], name: "Petit Cookie" },
     ];
 
+    // Insert documents into the restaurants collection
     const result = await coll.insertMany(docs);
     // end data insertion
 
     // begin aggregation
+    // Define an aggregation pipeline with a match stage and a group stage
     const pipeline = [
         { $match: { categories: "Bakery" } },
         { $group: { _id: "$stars", count: { $sum: 1 } } }
     ];
 
+    // Execute the aggregation
     const aggCursor = coll.aggregate(pipeline);
+    
+    // Print the aggregated results
     for await (const doc of aggCursor) {
         console.log(doc);
     }
     // end aggregation
 }
+// Run the program and print thrown errors, then close the connection
 run().catch(console.dir).finally(() => client.close());