How can you ensure that a specific script in package.json runs only after another specified script has successfully completed?
- Using npm's pre and post scripts
- Using conditional statements in JavaScript
- It's not possible to achieve this in package.json
- By using a third-party package
In package.json, you can use pre and post scripts to define the order in which scripts should run. For example, if you want a script to run after another, you can use "pre": "npm run firstScript" and "post": "npm run secondScript". This ensures that secondScript runs after firstScript.
In Express.js, what does the next() function do in middleware?
- Ends the request-response cycle
- Sends an HTTP response
- Passes control to the next middleware function
- Logs a message to the console
In Express.js, the next() function is used in middleware to pass control to the next middleware function in the stack. It allows the request to continue processing through subsequent middleware functions. If you don't call next(), the request-response cycle may be terminated, and subsequent middleware or route handlers won't be executed.
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.
When designing a schema for a SQL database in Node.js, the ______ key is used to establish a relationship between two tables.
- Foreign
- Index
- Primary
- Composite
When designing a schema for a SQL database in Node.js, the Foreign Key is used to establish a relationship between two tables. It creates a link between a field in one table and the primary key of another table, enabling data integrity and referential integrity.
In JavaScript, the ______ property is used to set up inheritance between custom types.
- inherit
- prototype
- extend
- object
In JavaScript, the prototype property is used to set up inheritance between custom types. It allows one object to inherit properties and methods from another object. This is a fundamental concept in JavaScript's object-oriented programming model.
The concept of defining a blueprint for the data in the database is known as ________.
- Schema
- Query
- Index
- Aggregate
The concept of defining a blueprint for the data in the database is known as "Schema." A schema defines the structure, relationships, constraints, and integrity rules of the data stored in a database.
When an EventEmitter instance experiences an error, the typical event that is emitted is ______.
- 'error'
- 'exception'
- 'fail'
- 'warning'
In Node.js, when an EventEmitter instance experiences an error, the typical event that is emitted is 'error'. This event allows you to handle errors that occur within event listeners attached to the EventEmitter.
How does the closure concept relate to higher-order functions in JavaScript?
- Closures are only used in lower-order functions.
- Higher-order functions cannot create closures.
- Higher-order functions often return closures, allowing them to encapsulate and manage private data.
- Closures are unrelated to higher-order functions.
Closures and higher-order functions are closely related in JavaScript. Higher-order functions often return closures, which can encapsulate and manage private data, creating a powerful mechanism for maintaining state and data privacy.