In JavaScript, a function that is defined inside another function has access to the outer function's variables, forming a ________.
- Closure
- Enclosure
- Junction
- Intersection
In JavaScript, when a function is defined inside another function, it forms a "closure." A closure allows the inner function to access the outer function's variables even after the outer function has finished executing.
You are designing a system with heavy Read and Update operations on the database. Which database design strategy would you adopt to balance the load and ensure data consistency?
- Sharding
- Replication
- Denormalization
- Indexing
In a scenario with heavy Read and Update operations, sharding is a database design strategy where you distribute the data across multiple servers or nodes. This helps balance the load and improve Read performance. Sharding ensures data consistency by managing data distribution and replication across shards. Replication (Option 2) can improve Read performance but doesn't address balancing the load directly. Denormalization (Option 3) can help with Reads but may complicate data consistency. Indexing (Option 4) helps with Read performance but doesn't balance the load.
Which of the following is true regarding object keys in JavaScript?
- Object keys must be unique within an object.
- Object keys can only be of type string.
- Object keys are case-sensitive.
- Object keys can only be integers.
Object keys in JavaScript are case-sensitive. This means that keys with different letter casing (e.g., 'key' and 'Key') are considered distinct in an object. The other options do not accurately describe the behavior of object keys.
How can the async/await syntax be used with error handling mechanisms, like try/catch, to handle asynchronous errors?
- Wrap the entire async function body in a try/catch block
- Use await inside a try/catch block for each individual asynchronous operation
- Use async without try/catch for handling errors
- Use await without try/catch for handling errors
To handle asynchronous errors with async/await, you should use a try/catch block around each individual await operation. This allows you to catch and handle errors for specific asynchronous operations within the async function. Option A would catch errors for the entire function, which might not provide fine-grained error handling. Options C and D are incorrect approaches for error handling with async/await.
When designing a system with high-frequency Read operations, ______ the database can optimize performance by reducing the I/O operations on the database.
- Indexing
- Normalizing
- Caching
- Sharding
In systems with high-frequency Read operations, caching the database can optimize performance by reducing the I/O operations on the database server. Cached data can be quickly retrieved from memory, reducing the load on the underlying database.
You are building an Express.js application where you have to route requests based on the subdomain. What approach would you take to implement this routing behavior?
- Use middleware to parse the subdomain and route accordingly
- Create separate Express.js applications for each subdomain
- Define subdomain-specific routes using regular expressions
- Use query parameters to determine the subdomain
To route requests based on the subdomain in Express.js, the most common approach is to use middleware (Option 1) that parses the subdomain from the request and then routes the request accordingly. This allows for flexibility and maintainability. Creating separate applications for each subdomain (Option 2) can lead to code duplication and complexity. Defining subdomain-specific routes using regular expressions (Option 3) can be error-prone and less maintainable. Using query parameters (Option 4) is not a common or recommended way to handle subdomain routing.
Which grant type in OAuth 2.0 is suitable for machine-to-machine applications where a user is not involved?
- Client Credentials
- Authorization Code
- Implicit
- Resource Owner Password Credentials
The Client Credentials grant type in OAuth 2.0 is suitable for machine-to-machine (M2M) applications where there is no user involved. It allows an application to directly authenticate itself and obtain an access token. The other grant types involve user interaction and are not intended for M2M scenarios.
How can closures be utilized effectively for asynchronous programming in JavaScript?
- Closures are often used in asynchronous programming in JavaScript to capture variables that are needed later when an asynchronous operation completes. This helps in maintaining the context and avoiding callback hell. Closures can be used to create functions that wrap asynchronous operations, making the code more readable and maintainable.
- Closures are commonly used in asynchronous programming in JavaScript to maintain the state and context of a function across asynchronous operations. They can be used to create functions that encapsulate asynchronous logic, making code more modular and readable.
- Closures are a powerful tool in asynchronous programming in JavaScript. They can be used to capture the state and context of a function, allowing asynchronous operations to access and modify variables from their enclosing scope. This is useful for maintaining data integrity and managing complex asynchronous flows.
- In asynchronous programming in JavaScript, closures are often used to capture the state of a function and maintain context across asynchronous operations. This can help in avoiding callback hell and making asynchronous code more readable and modular.
Asynchronous Programming with Closures
How can you extract route parameters in Express.js from a route URL like "/users/:userId"?
- Using req.params.userId
- Using req.query.userId
- Using req.body.userId
- Using req.param.userId
In Express.js, you can extract route parameters using req.params.userId. Route parameters are specified in the URL path with a colon prefix, and you can access them using req.params. The other options are not the correct way to access route parameters.
Using label with break or continue provides more control over which part of the code to ________ or ________ in JavaScript.
- skip, execute
- terminate, run
- jump, skip
- stop, resume
Using labels with break or continue in JavaScript provides more control over which part of the code to skip or execute. Labels allow you to specify which loop or block of code should be affected by break or continue statements when dealing with nested loops or complex control flow.