CORS is a security feature implemented by ________.
- Web browsers
- Server-side frameworks
- Client-side libraries
- Database systems
CORS (Cross-Origin Resource Sharing) is a security feature implemented by web browsers. It allows or restricts web applications running at one origin (domain) to make requests for resources located on a different origin.
How can cache stampede be mitigated in high-traffic applications?
- By using a cache eviction policy
- By implementing cache sharding
- By adding more cache nodes
- By using cache warming techniques
Cache stampede in high-traffic applications can be mitigated by using cache warming techniques. Cache warming involves preloading the cache with frequently accessed data, reducing the likelihood of cache misses and stampedes during high traffic.
You are experiencing slow query performance on a large dataset with millions of records. How would you identify and optimize the slow-performing queries?
- Use an Object-Relational Mapping (ORM) library
- Implement pagination for query results
- Create proper database indexes
- Increase server RAM
To optimize slow-performing queries on a large dataset, creating proper database indexes is crucial. Indexes can significantly speed up query performance by allowing the database to quickly locate relevant data. Options A and B might help with other aspects but do not directly address query performance. Increasing server RAM may not always resolve query performance issues related to large datasets.
In what scenarios would using object mode in streams be appropriate in Node.js?
- When dealing with binary data
- When processing large text files
- When working with complex JavaScript objects
- When reading from a database
Using object mode in streams is appropriate when you want to work with complex JavaScript objects as chunks, rather than raw binary or text data. It allows you to pass objects between streams without serialization. The other options do not typically require object mode.
You are tasked with merging multiple source objects into a single target object, ensuring that properties from the latest source overwrite those in the target. Which operator would you use, and how would you apply it to accomplish this task?
- Object.assign(target, ...sources);
- target << sources;
- target.merge(sources);
- target.spread(...sources);
To merge multiple source objects into a single target object in JavaScript and ensure that properties from the latest source overwrite those in the target, you would use the Object.assign() method. The ...sources syntax spreads the source objects into the Object.assign() method, accomplishing the task efficiently. The other options are not valid for this operation.
The concept of Non-Blocking I/O in Node.js is primarily built around the ________ paradigm.
- Asynchronous
- Synchronous
- Blocking
- Multithreading
The concept of Non-Blocking I/O in Node.js is primarily built around the "Asynchronous" paradigm. It allows I/O operations to occur without waiting for each other, enhancing efficiency and responsiveness in handling multiple requests concurrently.
How does the Event Loop mechanism in Node.js contribute to its non-blocking I/O feature, impacting performance positively?
- It uses multi-threading to execute I/O operations concurrently.
- It queues I/O operations and executes them in a single thread, preventing blocking.
- It blocks the execution until I/O operations are complete.
- It relies on external libraries for I/O, reducing performance.
Node.js uses an event loop to queue I/O operations and execute them asynchronously in a single thread, preventing blocking and maximizing performance. The other options describe incorrect behaviors or consequences of the event loop mechanism.
In JavaScript, when destructuring an object, the … (three dots) is called the ______ operator.
- Spread
- Assign
- Rest
- Merge
In JavaScript, when destructuring an object, the three dots (...) are called the "Spread" operator. The spread operator is used to unpack elements from an array or properties from an object.
How can you implement a custom writable stream in Node.js?
- util.promisify
- stream.pipeline
- Writable class
- Readable class
To implement a custom writable stream in Node.js, you should extend the Writable class and implement its _write method. This method is responsible for processing and writing data to the stream. The other options are not used for creating custom writable streams.
You are developing a JavaScript library that will be used by other developers. How can ESLint help in ensuring that the code is error-free and adheres to best practices before being published?
- ESLint cannot help in library development.
- Use ESLint to identify and fix coding errors, enforce coding standards, and ensure best practices are followed.
- Rely on user feedback after publishing the library to identify and fix issues.
- Hire a dedicated code reviewer to manually inspect the code.
ESLint can be a valuable tool in library development. It helps identify and fix coding errors, enforces coding standards, and ensures best practices are followed, reducing the likelihood of issues arising after publication. Relying solely on user feedback or manual code inspection may lead to post-release issues.