Which of the following is a suitable method to prevent variable leakage in the global scope?
- Using the var keyword to declare variables.
- Using immediately-invoked function expressions (IIFE).
- Using global variables exclusively.
- Using let and const keywords to declare variables.
Using immediately-invoked function expressions (IIFE) is a common technique to prevent variable leakage into the global scope. It encapsulates variables within a function scope, avoiding global pollution. The other options do not address this concern effectively.
How can you install ESLint in your Node.js project?
- Using npm or yarn: npm install eslint --save-dev or yarn add eslint --dev
- Downloading it from the official website
- Installing it globally using npm install -g eslint
- Adding it directly to your HTML file
You can install ESLint in your Node.js project using npm or yarn by running the command npm install eslint --save-dev or yarn add eslint --dev. This ensures that ESLint is added as a development dependency for your project.
You are tasked with developing a logging system for an Express.js application to log every incoming request. How would you implement middleware to log the details of every request made to the application?
- Create a middleware function that logs request details and use app.use to apply it globally to all routes.
- Include logging code within each route handler to log request details individually.
- Use a third-party logging library like Morgan and configure it within your Express.js application.
- Use JavaScript's built-in console.log within each route to log request details.
To log details of every incoming request in an Express.js application efficiently, you should create a dedicated middleware function that logs request details and use app.use to apply it globally to all routes. This centralizes logging and avoids duplicating code in each route handler. The other options are either less efficient or not recommended for production applications.
You are configuring a Node.js project and want to ensure that a certain command runs before your tests run each time. How would you configure this using the package.json file?
- Use the "pretest" script in the "scripts" section of the package.json file to specify the command that should run before tests.
- Include the command in the "description" field of the package.json file.
- Create a separate pretest.json configuration file.
- Use a comment in the test file to specify the pretest command.
To ensure a certain command runs before tests each time, you should use the "pretest" script in the "scripts" section of the package.json file. This script will be executed automatically before running tests when the npm test command is invoked. The other options are not standard ways to configure pretest actions.
You are developing a suite of unit tests for a service that interacts with an external API. How would you employ mocking and stubbing to ensure the tests are isolated and reliable?
- Mock the external API calls to simulate responses
- Stub all internal functions used in the service
- Avoid mocking and use real external API calls
- Mock only the database interactions
In unit testing, it's crucial to isolate the code being tested. To ensure tests are isolated and reliable when dealing with an external API, you should mock the external API calls. This allows you to control the responses and not rely on external services during tests. Stubbing internal functions is not the primary approach for isolating external API calls. Avoiding mocking by using real API calls can lead to unreliable and slow tests. Mocking the database, in this case, is unnecessary.
The fs.watch method is used to watch for changes in a file or a directory but may not be consistent across platforms due to its reliance on ______.
- inotify
- polling
- event-driven
- file system events
The fs.watch method relies on polling on some platforms to detect file and directory changes. This polling approach may not be consistent across platforms and can have performance implications.
You are tasked with improving the performance of a database that experiences heavy read and write operations. How would you balance the use of indexing to improve read performance while minimizing the impact on write performance?
- Add Indexes to All Columns for Faster Reads
- Use Covering Indexes for Frequently Queried Columns
- Implement Partitioned Tables to Isolate Write-Intensive Data
- Regularly Rebuild All Indexes for Maximum Performance
To balance the use of indexing in a database with heavy read and write operations, it's crucial to use Covering Indexes for frequently queried columns. These indexes include all the necessary data for the query, reducing the need to access the main table. Implementing Partitioned Tables can isolate write-intensive data from read-intensive data, improving write performance. Adding indexes to all columns and regularly rebuilding all indexes can lead to unnecessary overhead and hinder write performance.
Which method in Express.js is used to serve static files?
- app.static()
- app.useStatic()
- app.serveStatic()
- app.use()
In Express.js, the app.use(express.static()) method is used to serve static files. This method allows you to specify a directory from which Express should serve static assets like images, CSS, and JavaScript. The other options are not valid methods for serving static files in Express.
In Express.js, the ______ method is commonly used to protect routes and ensure that only authenticated users can access them.
- authenticate
- secure
- authorize
- validate
In Express.js, the authorize method is commonly used to protect routes and ensure that only authenticated users can access them. This is often achieved through middleware functions that check for authentication and authorization before allowing access. The other options may not be standard methods for this purpose in Express.js.
In the context of security, what does the principle of "least privilege" mean?
- Giving users the fewest privileges necessary to perform their tasks
- Giving users all possible privileges
- Giving administrators fewer privileges than regular users
- Giving privileges based on user seniority
The principle of "least privilege" means giving users the fewest privileges necessary to perform their tasks. This reduces the risk of unauthorized access and potential security breaches. The other options do not align with this security principle.