What is a closure in JavaScript?
- A closure is a built-in JavaScript function
- A closure is a function that has access to the variables from its containing function, even after the containing function has finished executing.
- A closure is a special type of variable in JavaScript
- A closure is a function that is defined within another function.
A closure in JavaScript is a function that has access to the variables from its containing function, even after the containing function has finished executing. This is a fundamental concept in JavaScript for maintaining data encapsulation and is often used for creating private variables and functions.
How does the 'events' module in Node.js help in managing asynchronous operations?
- It provides a way to pause and resume asynchronous tasks.
- It allows you to execute asynchronous tasks in parallel.
- It provides an event-driven architecture for handling asynchronous operations.
- It enables synchronous execution of asynchronous tasks.
The 'events' module in Node.js is designed to facilitate event-driven programming, allowing you to handle asynchronous operations by defining event listeners and emitters. It does not provide mechanisms for pausing, resuming, or executing tasks synchronously.
A ______ request is sent by the browser before the actual request to check the server’s CORS policy.
- preflight
- probe
- inspection
- initiation
A "preflight" request is sent by the browser before the actual cross-origin request to check the server's CORS policy. It helps the browser determine whether the actual request is safe to send and whether the server will allow it.
During the development of a Node.js application, you realize that multiple packages are not compatible with each other due to different required versions. How would you resolve the incompatibility between these packages?
- Delete one of the incompatible packages
- Use a tool like npm-shrinkwrap to lock package versions
- Update all packages to their latest versions
- Modify your code to work with the conflicting versions
To resolve package version incompatibility, you can use a tool like npm-shrinkwrap to lock package versions, ensuring that all team members use the same versions. Deleting packages or updating them indiscriminately can introduce issues.
The process object in Node.js emits a ______ event when the Node.js process is about to exit.
- beforeExit
- exit
- shutdown
The process object in Node.js emits the beforeExit event just before the Node.js process is about to exit. This event allows you to perform cleanup tasks before the process terminates.
When using semantic versioning, what is the recommended way to handle deprecations?
- Deprecations should be documented in the code comments only.
- Deprecations should be ignored as they don't fit into semantic versioning.
- Deprecations should be marked as 'deprecated' in code comments and, if necessary, in the README or documentation.
- Deprecations should be removed from the codebase without any notice.
In semantic versioning, it's recommended to mark deprecations as 'deprecated' in code comments and, when applicable, in the README or documentation. This helps users of the library or package understand what's changing and how it might impact their code.
The process of rewriting a SQL query to improve its efficiency without changing its behavior is known as ________.
- Query Tuning
- Query Optimization
- Query Refactoring
- Query Modification
The process of rewriting a SQL query to improve its efficiency without changing its behavior is known as "Query Optimization." This involves making changes to the query or its execution plan to make it faster while still returning the same results.
What will be the default encoding when converting a buffer to a string in Node.js?
- utf-8
- binary
- ascii
- base64
When converting a buffer to a string in Node.js, the default encoding is utf-8. It's important to specify the encoding when performing this conversion, as using the wrong encoding can lead to incorrect results or data corruption.
Which command is used to install Express in your Node.js project?
- npm install express
- npm express install
- install -g express
- node express-install
To install the Express framework in your Node.js project, you should use the command npm install express. This command will download and install the Express package and its dependencies. The other options are not valid ways to install Express.
You are building an API using Express.js, and you want to ensure that the client receives meaningful error messages when something goes wrong. How would you structure your error-handling middleware to achieve this?
- Send status code 200 for all errors
- Use generic error messages for all errors
- Create custom error classes and send detailed error messages
- Log errors to the console only
To ensure that clients receive meaningful error messages, you should structure your error-handling middleware to create custom error classes and send detailed error messages. This allows you to provide specific information about the nature of the error, making it easier for clients to understand and handle errors gracefully. Sending generic error messages or using status code 200 for all errors would not provide meaningful information to clients. Logging errors to the console only is not sufficient for client communication.