docsp-32718 - add comments (#770)

source/code-snippets/crud/arrayFilters.js

@@ -7,9 +7,12 @@ const client = new MongoClient(uri);
 
 async function printData() {
   try {
+
+    // Get the database and collection on which to run the operation
     const myDB = client.db("test");
     const myColl = myDB.collection("testColl");
 
+    // Print all documents 
     console.log(JSON.stringify(await myColl.find().toArray()));
   } finally {
     await client.close();
@@ -18,18 +21,28 @@ async function printData() {
 
 async function runFirstArrayElement() {
   try {
+
+    // Get the database and collection on which to run the operation
     const myDB = client.db("test");
     const myColl = myDB.collection("testColl");
 
+    // Print the result
     console.log(JSON.stringify(await myColl.find().toArray()));
 
     // start firstArrayElement example
+    // Query for all elements in entries array where the value of x is a string
     const query = { "entries.x": { $type : "string" } };
+
+    // On first matched element, increase value of y by 33
     const updateDocument = {
       $inc: { "entries.$.y": 33 }
     };
+
+    // Execute the update operation
     const result = await myColl.updateOne(query, updateDocument);
     // end firstArrayElement example
+
+    // Print all documents
     console.log(result.modifiedCount);
     console.log(JSON.stringify(await myColl.find().toArray()));
   } finally {
@@ -39,19 +52,30 @@ async function runFirstArrayElement() {
 
 async function runAllArrayElements() {
   try {
+
+    // Get the database and collection on which to run the operation
     const myDB = client.db("test");
     const myColl = myDB.collection("testColl");
 
+    // Print all documents 
     console.log(JSON.stringify(await myColl.find().toArray()));
 
     // start allArrayElement example
+    // Query for all documents where date is the string "5/15/2023"
     const query = { date: "5/15/2023" };
+
+    // For each matched document, remove duration field from all entries in calls array 
     const updateDocument = {
       $unset: { "calls.$[].duration": "" }
     };
+
+    // Execute the update operation
     const result = await myColl.updateOne(query, updateDocument);
     // end allArrayElement example
+
     console.log(result.modifiedCount);
+
+    // Print all documents 
     console.log(JSON.stringify(await myColl.find().toArray()));
   } finally {
     await client.close();
@@ -60,16 +84,24 @@ async function runAllArrayElements() {
 
 async function arrayFiltersIdentifier() {
   try {
+
+    // Get the database and collection on which to run the operation
     const myDB = client.db("test");
     const myColl = myDB.collection("testColl");
 
+    // Print all documents 
     console.log(JSON.stringify(await myColl.find().toArray()));
 
     // start arrayFiltersIdentifier example
+    // Query for all documents where date is the string "11/12/2023"
     const query = { date: "11/12/2023" };
+
+    // For each matched document, change the quantity of items to 2 
     const updateDocument = {
       $mul: { "items.$[i].quantity": 2 }
     };
+
+    // Update only non-oil items used for fried rice 
     const options = {
       arrayFilters: [
         {
@@ -78,10 +110,13 @@ async function arrayFiltersIdentifier() {
         }
       ]
     };
+
+    // Execute the update operation
     const result = await myColl.updateOne(query, updateDocument, options);
     // end arrayFiltersIdentifier example
     console.log(result.modifiedCount);
 
+    // Print all documents 
     console.log(JSON.stringify(await myColl.find().toArray()));
   } finally {
     await client.close();

source/code-snippets/indexes/text.js

@@ -10,6 +10,7 @@ const client = new MongoClient(uri);
 async function run() {
   try {
     // begin-idx
+    // Get the database and collection on which to create the index 
     const myDB = client.db("testDB");
     const myColl = myDB.collection("blogPosts");
 
@@ -23,8 +24,13 @@ async function run() {
     console.log(`Index created: ${result}`);
 
     // begin-query
+    // Query for documents where body or title contain "life ahead"
     const query = { $text: { $search: "life ahead" } };
+
+    // Show only the title field
     const projection = { _id: 0, title: 1 };
+
+    // Execute the find operation
     const cursor = myColl.find(query).project(projection);
     // end-query
     for await (const doc of cursor) {

source/code-snippets/monitoring/cpm-subscribe.js

@@ -8,6 +8,8 @@ const client = new MongoClient(uri);
 
 // Replace <event name> with the name of the event you are subscribing to
 const eventName = "<event name>";
+
+// Subscribe to the event
 client.on(eventName, (event) =>
   console.log("\nreceived event:\n", event)
 );

source/code-snippets/usage-examples/distinct.js

@@ -7,18 +7,21 @@ const client = new MongoClient(uri);
 
 async function run() {
   try {
-    // define a database and collection on which to run the method
+
+    // Get the database and collection on which to run the operation
     const database = client.db("sample_mflix");
     const movies = database.collection("movies");
 
-    // specify the document field
+    // Specify the document field to find distinct values for
     const fieldName = "year";
 
-    // specify an optional query document
+    // Specify an optional query document to narrow results
     const query = { directors: "Barbra Streisand" };
 
+    // Execute the distinct operation
     const distinctValues = await movies.distinct(fieldName, query);
 
+    // Print the result
     console.log(distinctValues);
   } finally {
     await client.close();

source/code-snippets/usage-examples/find.js

@@ -7,26 +7,30 @@ const client = new MongoClient(uri);
 
 async function run() {
   try {
+
+    // Get the database and collection on which to run the operation
     const database = client.db("sample_mflix");
     const movies = database.collection("movies");
 
-    // query for movies that have a runtime less than 15 minutes
+    // Query for movies that have a runtime less than 15 minutes
     const query = { runtime: { $lt: 15 } };
 
     const options = {
-      // sort returned documents in ascending order by title (A->Z)
+      // Sort returned documents in ascending order by title (A->Z)
       sort: { title: 1 },
       // Include only the `title` and `imdb` fields in each returned document
       projection: { _id: 0, title: 1, imdb: 1 },
     };
 
+    // Execute query 
     const cursor = movies.find(query, options);
 
-    // print a message if no documents were found
+    // Print a message if no documents were found
     if ((await movies.countDocuments(query)) === 0) {
       console.log("No documents found!");
     }
 
+    // Print returned documents
     for await (const doc of cursor) {
       console.dir(doc);
     }

source/code-snippets/usage-examples/findOne.js

@@ -7,22 +7,25 @@ const client = new MongoClient(uri);
 
 async function run() {
   try {
+
+    // Get the database and collection on which to run the operation
     const database = client.db("sample_mflix");
     const movies = database.collection("movies");
 
     // Query for a movie that has the title 'The Room'
     const query = { title: "The Room" };
 
     const options = {
-      // sort matched documents in descending order by rating
+      // Sort matched documents in descending order by rating
       sort: { "imdb.rating": -1 },
       // Include only the `title` and `imdb` fields in the returned document
       projection: { _id: 0, title: 1, imdb: 1 },
     };
 
+    // Execute query
     const movie = await movies.findOne(query, options);
 
-    // since this method returns the matched document, not a cursor, print it directly
+    // Print the document returned by findOne()
     console.log(movie);
   } finally {
     await client.close();

source/code-snippets/usage-examples/insertMany.js

@@ -7,20 +7,25 @@ const client = new MongoClient(uri);
 
 async function run() {
   try {
+
+    // Get the database and collection on which to run the operation
     const database = client.db("insertDB");
     const foods = database.collection("foods");
 
-    // create an array of documents to insert
+    // Create an array of documents to insert
     const docs = [
       { name: "cake", healthy: false },
       { name: "lettuce", healthy: true },
       { name: "donut", healthy: false }
     ];
 
-    // this option prevents additional documents from being inserted if one fails
+    // Prevent additional documents from being inserted if one fails
     const options = { ordered: true };
 
+    // Execute insert operation
     const result = await foods.insertMany(docs, options);
+
+    // Print result
     console.log(`${result.insertedCount} documents were inserted`);
   } finally {
     await client.close();

source/code-snippets/usage-examples/replaceOne.js

@@ -7,17 +7,23 @@ const client = new MongoClient(uri);
 
 async function run() {
   try {
+
+    // Get the database and collection on which to run the operation
     const database = client.db("sample_mflix");
     const movies = database.collection("movies");
 
-    // create a query for a movie to update
+    // Create a query for documents where the title contains "The Cat from"
     const query = { title: { $regex: "The Cat from" } };
-    // create a new document that will be used to replace the existing document
+
+    // Create the document that will replace the existing document
     const replacement = {
       title: `The Cat from Sector ${Math.floor(Math.random() * 1000) + 1}`,
     };
 
+    // Execute the replace operation
     const result = await movies.replaceOne(query, replacement);
+
+    // Print the result 
     console.log(`Modified ${result.modifiedCount} document(s)`);
   } finally {
     await client.close();

source/fundamentals/crud/write-operations/embedded-arrays.txt

@@ -283,7 +283,7 @@ code:
    :language: javascript
    :start-after: start arrayFiltersIdentifier example
    :end-before: end arrayFiltersIdentifier example
-   :emphasize-lines: 3, 6-11
+   :emphasize-lines: 6, 11-16 
    :dedent:
 
 The update multiplied the ``quantity`` value by ``2`` for