In which format is image data usually sent to the server when uploading files in a web application?
- JSON
- XML
- Base64
- CSV
Image data is usually sent to the server in Base64 format when uploading files in a web application. This format allows binary data (like images) to be represented as a string, making it easier to transmit as part of an HTTP request. The other options (JSON, XML, and CSV) are not typically used for sending binary data like images.
Which of the following is a common technique used for optimizing database queries?
- Query caching
- Adding more indexes
- Increasing database complexity
- Ignoring query performance
One common technique used for optimizing database queries is query caching. It involves storing frequently used query results in memory, reducing the need to re-execute the same query, and improving response times.
If a package is required for running the tests, it should ideally be listed under ________.
- devDependencies
- dependencies
- peerDependencies
- optionalDependencies
If a package is required for running the tests, it should ideally be listed under devDependencies. This ensures that the testing dependencies are only installed during development and testing phases, keeping the production environment clean from unnecessary packages.
You are designing a logging system in Node.js where multiple loggers are listening to logging events. How would you manage and optimize the event listeners to avoid potential memory leaks?
- event.setMaxListeners(1)
- event.on('log', loggerCallback)
- event.prependListener('log', loggerCallback)
- event.removeListener('log', loggerCallback)
To avoid memory leaks when multiple loggers are listening to logging events, it's crucial to remove listeners when they are no longer needed. The event.removeListener() method should be used to remove specific listeners, ensuring that you free up memory and resources when loggers are no longer required. The other options are related to listener management but do not directly address memory leaks.
You are developing an Express application that requires user authentication. How do you ensure that user credentials are secured, and sessions are managed effectively across different routes?
- Use a secure authentication library like Passport.js, store user credentials securely by hashing and salting passwords, and implement session management with the express-session middleware.
- Store user credentials in plain text for simplicity, use client-side storage for session management, and avoid encrypting sensitive data to reduce overhead.
- Implement a custom authentication mechanism using base64 encoding for user credentials, and manage sessions by storing them in a global JavaScript object.
- Use HTTP Basic Authentication for user login and manage sessions by storing user information in cookies without encryption.
To ensure secure user authentication and session management in an Express application, it's crucial to use a secure authentication library like Passport.js, securely store user credentials, and utilize a trusted session management middleware like express-session. Options 2, 3, and 4 are insecure and not recommended practices.
Why might a developer list a package as a devDependency instead of a dependency?
- A devDependency is needed only during development, not in production.
- A devDependency is automatically updated more frequently than a regular dependency.
- A devDependency reduces the overall bundle size of the application.
- A devDependency allows other developers to contribute to the project.
Developers list a package as a devDependency when it's required during development but not needed in production. This helps to keep the production build smaller and avoids unnecessary dependencies.
In Mocha, to perform cleanup activities after all the test cases in a suite have run, the ______ hook is used.
- after
- afterEach
- teardown
- suiteTeardown
In Mocha, the after hook is used to perform cleanup activities after all the test cases in a suite have run. It runs once after all test cases within the suite. The other options (afterEach, teardown, and suiteTeardown) represent different hook names or are not used for this specific purpose in Mocha.
When implementing file uploads in a serverless architecture, it is often beneficial to use ______ to handle file processing and transformations.
- AWS Lambda
- Docker Containers
- Kubernetes
- AWS S3
When implementing file uploads in a serverless architecture, it is often beneficial to use "AWS Lambda" to handle file processing and transformations. AWS Lambda allows you to execute code in response to events and can be triggered by file uploads. Docker containers and Kubernetes are containerization technologies, and AWS S3 is a storage service, but they are not typically used for serverless file processing.
When using the fs module to write data to a file, what considerations must be taken into account regarding concurrency?
- Node.js automatically handles concurrency
- Concurrency is not a concern when using fs
- Ensure proper locking mechanisms for concurrent writes
- Concurrency is only an issue with network operations
When working with the fs module, you must consider concurrency, especially when multiple processes or threads are writing to the same file simultaneously. It's important to implement proper locking mechanisms, such as file locking, to prevent data corruption. Node.js does not handle concurrency automatically.
Which object is primarily used to emit events in Node.js?
- Emitter
- EventEmitter
- EventObject
- EventHandler
In Node.js, the primary object used to emit events is EventEmitter. It's a built-in module that provides the core functionality for event-driven programming. Options A, C, and D are not the standard objects for emitting events in Node.js.