Which of the following is a common technique used for implementing full-text search in databases?
- Regular Expressions
- Binary Search
- Inverted Index
- Depth-First Search
A common technique for implementing full-text search in databases is the use of an inverted index. This index stores a list of words or terms along with the locations where they appear in the documents, making it efficient for searching large volumes of text. Regular expressions, binary search, and depth-first search are not typically used for full-text search in databases.
How does the use of subqueries impact the performance of SQL queries, and how can it be optimized?
- Subqueries can slow down SQL queries significantly. They execute for each row in the outer query result and may lead to performance bottlenecks. Optimization techniques include using JOINs, EXISTS, or rewriting queries as JOINs, ensuring indexes on relevant columns, and limiting the result set size.
- Subqueries have no impact on SQL query performance.
- Subqueries always improve SQL query performance.
- Subqueries should be avoided, but if used, no optimization is possible.
Subqueries can impact SQL query performance negatively if not used carefully. They can lead to increased query execution times, and optimizing them involves using appropriate techniques to minimize their impact.
You have been assigned to optimize the CRUD operations of a microservices-based application where each microservice handles its own database. How would you ensure the consistency and integrity of data across different microservices while performing Create and Update operations?
- Implement a distributed transaction coordinator
- Use REST APIs for communication
- Share a centralized database
- Implement message queues
To ensure the consistency and integrity of data across different microservices in a microservices-based application, implementing a distributed transaction coordinator (Option 1) is a suitable approach. This coordinator can manage transactions across multiple microservices, ensuring that Create and Update operations either succeed or fail together, preserving data integrity. Using REST APIs (Option 2) for communication is a common practice but doesn't guarantee transactional consistency. Sharing a centralized database (Option 3) can create tight coupling and hinder the benefits of microservices. Implementing message queues (Option 4) helps with asynchronous communication but doesn't inherently guarantee data consistency across microservices.
How does the spread operator behave when used with JavaScript objects that have the same properties?
- It merges the properties, with the values of the second object overwriting the values of the first object.
- It throws an error because objects with the same properties cannot be spread.
- It combines the properties into an array.
- It creates a new object with the properties of the first object only.
When the spread operator (...) is used on objects with the same properties, it merges the properties, with the values of the second object overwriting the values of the first object. This behavior is known as object property spreading.
When using Promise.allSettled, the returned array consists of objects, each having a status property that can either be 'fulfilled' or ________.
- 'completed'
- 'resolved'
- 'rejected'
- 'done'
When using Promise.allSettled, the status property of each object in the returned array can either be 'fulfilled' or 'rejected,' depending on the outcome of the individual Promises in the input array.
In a Node.js module, properties added to the global object can be accessed from ________.
- anywhere in the module
- only within the module
- any other module
Properties added to the global object in a Node.js module can be accessed from anywhere in the module, making them globally accessible within that module.
What is the significance of test coverage in a codebase, and how does it impact the development process?
- Test coverage measures the number of lines of code tested; High test coverage guarantees a bug-free codebase; Test coverage is irrelevant for development.
- Test coverage measures the percentage of code executed by tests; It helps identify untested code paths and potential bugs; High test coverage is a valuable metric but doesn't guarantee bug-free code.
- Test coverage measures the number of test cases written; High test coverage means exhaustive testing and zero defects; Test coverage should be minimized to save development time.
- Test coverage is the number of test tools used; High test coverage indicates a comprehensive testing suite; Test coverage depends on project size.
Test coverage measures the percentage of code executed by tests. It helps identify untested code paths, improving code quality. However, it does not guarantee a bug-free codebase, as it depends on the quality of the tests. The other options provide inaccurate definitions or misconceptions about test coverage.
When creating a custom error class in Express.js, it should extend the built-in ______ class.
- Error
- HttpException
- AppError
- CustomError
When creating a custom error class in Express.js, it should extend the built-in Error class. This allows you to leverage the error handling capabilities provided by JavaScript and Express.js. Extending other classes like HttpException, AppError, or CustomError is not a standard practice for custom error classes in Express.js.
In the http module, the ______ event of the server object is emitted when the server closes.
- close
- end
- disconnect
- terminate
In the http module, the close event of the server object is emitted when the server closes. This event allows you to perform cleanup or take action when the server is shutting down. The other options (end, disconnect, terminate) do not represent the server closing event in the HTTP module.
The for…of statement creates a loop iterating over ________ objects in JavaScript.
- enumerable
- all
- array-like
- visible
The for...of statement in JavaScript creates a loop that iterates over array-like objects, which include arrays, strings, maps, sets, and other objects that have iterable properties. It's particularly useful for iterating over the values of such objects.