Why is caching used in web applications?
- To reduce server load and improve performance
- To increase server load and slow down performance
- To secure user data
- To display error messages
Caching in web applications is used to reduce server load and improve performance by storing frequently accessed data, such as web pages or database query results, so that it can be quickly retrieved without the need to regenerate it. Caching helps in minimizing the need for redundant processing and data retrieval.
In semantic versioning, what does a change in the 'patch' version (e.g. 1.2.3) typically indicate?
- Bug fixes
- New features
- Backwards-incompatible changes
- Minor improvements
In SemVer, a change in the 'patch' version indicates that there have been backwards-compatible bug fixes. This means that the changes made in this version should not break existing functionality and are intended to address issues and improve stability.
You are working on a web scraping tool. You have multiple URLs to fetch data from, but you want to proceed with the next steps only when data from all URLs are fetched successfully. How would you achieve this using Promises?
- Use Promise.all()
- Use Promise.race()
- Use async/await without Promise.all()
- Use multiple then() blocks
To proceed with the next steps only when data from all URLs is fetched successfully, you should use Promise.all(). This method takes an array of Promises and resolves only when all of them resolve successfully. Promise.race() resolves on the first success, which is not suitable for this scenario. Using async/await without Promise.all() may not ensure that all URLs are successfully fetched before proceeding.
You are developing a large-scale application using Pug as a template engine, and you need to create reusable components. How would you create a reusable navigation component in Pug that can be included in multiple views?
- Define the navigation component in a separate Pug file, and then include it using the include keyword in each view where you want to use it.
- Create a JavaScript function to generate the navigation HTML and call this function in each view's Pug template.
- Embed the navigation HTML directly in each view's Pug template to ensure it's customized for each page.
- Use an external CSS library to create a navigation menu and import it into your Pug templates.
To create a reusable navigation component in Pug, you should define the navigation component in a separate Pug file and then include it using the include keyword in each view where you want to use it. This approach promotes code reusability and maintainability.
How does the switch statement compare the switch expression with the case expressions in JavaScript?
- It uses strict equality (===) for comparison.
- It uses loose equality (==) for comparison.
- It uses comparison operators (<, >, etc.) for comparison.
- It uses regular expressions for comparison.
In JavaScript, the switch statement uses strict equality (===) to compare the switch expression with the case expressions. This means it checks both the value and the type of the expressions. Using loose equality (==) is not the standard behavior for a switch statement.
In Express.js, which middleware is used to handle errors?
- bodyParser
- errorHandler
- static
- router
In Express.js, the errorHandler middleware is used to handle errors. It's specifically designed to catch errors that occur during request processing and handle them gracefully. The other options are used for different purposes, such as parsing request bodies (bodyParser), serving static files (static), and defining routes (router).
How does denormalization in database schema design affect data redundancy and read performance?
- Decreases data redundancy and improves read performance
- Increases data redundancy and improves read performance
- Decreases data redundancy and decreases read performance
- Increases data redundancy and decreases read performance
Denormalization in database schema design increases data redundancy but can improve read performance. By storing redundant data, queries can often be faster since they require fewer joins. However, this comes at the cost of increased storage requirements and potential data update anomalies.
How does the try...catch statement work in asynchronous operations in Node.js?
- It cannot be used with asynchronous operations.
- It catches exceptions asynchronously with the help of callbacks.
- It works synchronously and blocks the event loop.
- It is only applicable to synchronous code.
In Node.js, the try...catch statement can be used with asynchronous operations, but it doesn't catch exceptions directly in asynchronous callbacks. Instead, it catches exceptions that occur during the setup of asynchronous operations or in the main event loop. It doesn't block the event loop.
How can LIMIT and OFFSET be used effectively to optimize SQL queries?
- Use LIMIT to specify the maximum number of rows to retrieve and OFFSET to skip a certain number of rows.
- Use OFFSET to specify the maximum number of rows to retrieve and LIMIT to skip a certain number of rows.
- Use LIMIT and OFFSET together to retrieve all rows in a table.
- Use LIMIT and OFFSET to restrict the number of columns retrieved in a query.
LIMIT is used to restrict the number of rows in the result set, while OFFSET is used to skip a certain number of rows. This is helpful for paginating results and optimizing queries when you don't need to retrieve the entire dataset.
Which of the following strategies can be used to efficiently serve static assets and optimize performance?
- Caching static assets at the server-side.
- Using long, descriptive file names for static assets.
- Serving static assets through a Content Delivery Network (CDN).
- Storing static assets in a database.
Serving static assets through a Content Delivery Network (CDN) is an efficient strategy to optimize performance by distributing assets across geographically distributed servers, reducing latency and improving load times. The other options either don't directly address performance optimization or provide incorrect methods.