You are building a real-time data processing system where tasks are dependent on the completion of previous tasks. How would you structure your Promises/async functions to ensure the sequence is maintained?
- Using async/await
- Using Promise.then()
- Using Promise.race()
- Using setTimeout()
To ensure the sequence of tasks is maintained in a real-time data processing system, you should structure your code using async/await. This allows you to write asynchronous code in a more synchronous style, ensuring that each task awaits the completion of the previous one. The other options are not typically used for sequential task execution.
Can you modify the package.json file after it has been created by the npm init command?
- Yes, but only with admin privileges
- No, it's read-only
- Yes, it can be edited anytime
- Yes, but only during project initialization
Yes, you can modify the package.json file after it has been created by the npm init command. It's a JSON configuration file that stores information about your project, and you can update it to add dependencies, scripts, and other project-related settings. It's a fundamental part of managing Node.js projects.
You are tasked with evolving the schema of a critical, high-traffic database while minimizing downtime and data inconsistency. What strategies would you employ to safely apply schema migrations?
- Use database migration tools with rollback support.
- Apply schema changes during off-peak hours.
- Utilize database versioning and backward-compatible changes.
- Pause the database for maintenance during schema updates.
Option (1) is a common approach as it allows you to apply changes with rollback capabilities. Option (2) is valid to minimize the impact on users. Option (3) is also important, using versioning and backward-compatible changes ensures a smoother transition. Option (4) is typically not recommended, as it causes downtime.
You are tasked with developing a file upload module in Node.js. The files uploaded by users are binary data. How would you handle the incoming binary data to ensure data integrity and optimal resource utilization?
- Use streams to handle and process binary data in chunks
- Read the entire binary data into memory before processing
- Convert binary data to hexadecimal for storage
- Store binary data in a JSON format
To ensure data integrity and optimal resource utilization when handling binary data in a file upload module, it's best to use streams to handle and process binary data in chunks. This approach minimizes memory usage and ensures data integrity. Reading the entire binary data into memory is not efficient, and the other options are not suitable for storing binary data.
You are working on a project where you need to load different modules based on user actions dynamically. What approach should you take to load the modules only when necessary?
- Use synchronous module loading.
- Use Webpack to bundle all modules upfront.
- Employ dynamic import statements.
- Load all modules at application startup.
To load modules dynamically based on user actions, you should employ dynamic import statements (Option c). Dynamic imports allow you to load modules asynchronously and only when they are needed, improving the efficiency of your application. Synchronous loading (Option a) and loading all modules upfront (Option d) are counterproductive for this scenario. While Webpack bundling (Option b) can be useful for other purposes, it doesn't address the need for dynamic loading.
How does JavaScript’s prototypal inheritance differ from classical inheritance models?
- JavaScript uses delegation-based inheritance, where objects inherit from other objects directly, not from classes.
- JavaScript uses class-based inheritance like many other programming languages.
- JavaScript's inheritance is more rigid and less flexible compared to classical models.
- JavaScript's inheritance is limited to only built-in objects.
JavaScript's prototypal inheritance differs from classical inheritance models by using delegation-based inheritance. Instead of inheriting from classes, objects inherit directly from other objects, which is more flexible and dynamic.
In a NoSQL database like MongoDB, how are schemas defined and enforced?
- Schemas are strictly enforced before data insertion
- Schemas are defined using SQL
- Schemas are flexible and can evolve with data
- Schemas are predefined and cannot change
In NoSQL databases like MongoDB, schemas are flexible and can evolve with data. There's no strict enforcement of schemas before data insertion, allowing for schema-less data storage. This flexibility is one of the key features of NoSQL databases, making them suitable for handling unstructured or semi-structured data.
In Node.js, what is the purpose of the process.on('uncaughtException', handler) method?
- To catch exceptions and continue program execution
- To exit the Node.js process on any unhandled exception
- To display uncaught exceptions in the console
- To handle exceptions within a specific function
The process.on('uncaughtException', handler) method in Node.js is used to capture unhandled exceptions and prevent the Node.js process from crashing. It allows you to specify a custom handler function to handle these exceptions gracefully. The other options do not accurately describe the purpose of this method.
How can you create a deep copy of an object in JavaScript?
- JSON.parse(JSON.stringify(object))
- object.copy()
- deepCopy(object)
- Object.clone(object)
To create a deep copy of an object in JavaScript, you can use JSON.parse(JSON.stringify(object)). This method serializes the object to a JSON string and then parses it back into a new object, effectively creating a deep copy. The other options are not valid for deep copying objects.
In the context of closures, what is meant by the term 'lexical scoping' in JavaScript?
- Lexical scoping, also known as static scoping, means that the scope of a variable is determined by its position within the source code, and it is fixed at the time of the variable's definition. In JavaScript, closures have lexical scoping, which means they capture variables from the outer function based on where they are defined in the code, not where they are executed.
- Lexical scoping, also called static scoping, refers to the way variables are resolved in a program. In JavaScript closures, lexical scoping means that the scope of a variable is determined by its location in the source code, and it remains fixed once the function is defined.
- Lexical scoping, often referred to as static scoping, is a feature of closures in JavaScript. It means that a closure captures variables from its surrounding context based on their lexical location, not their runtime values. This allows closures to access variables even after the outer function has completed execution.
- In JavaScript closures, lexical scoping means that the scope of a variable is determined by its position in the code when the closure is defined, not when it is executed. This ensures that closures capture the correct variables from their enclosing scope.
Closures and Lexical Scoping
Which of the following is true about the prototype chain in JavaScript?
- The prototype chain allows access to properties and methods of an object's prototype and its prototype's prototype, forming a chain.
- The prototype chain only includes direct parent objects.
- The prototype chain is static and cannot be modified dynamically.
- The prototype chain is not used in JavaScript.
The prototype chain in JavaScript allows access to properties and methods of an object's prototype, its prototype's prototype, and so on, forming a chain. It is a fundamental concept in JavaScript's object-oriented programming.
To implement an authorization mechanism in Express.js effectively, developers often use ______ to manage user roles and permissions.
- Passport.js
- Express Passport
- Sequelize
- Mongoose
To implement an authorization mechanism in Express.js effectively, developers often use Passport.js. Passport.js is a popular authentication middleware for Node.js that supports various authentication strategies and can be used to manage user roles and permissions effectively. Sequelize and Mongoose are libraries for working with databases and are not directly related to authorization in Express.js.