Which of the following is a practical use of closures in JavaScript?
- Implementing asynchronous operations like AJAX requests.
- Creating global variables for sharing data across different scripts.
- Defining functions with no parameters.
- Handling keyboard events in a web page.
Closures are often used in JavaScript to implement asynchronous operations like AJAX requests, where you want to maintain the context and state of the calling function. The other options are not practical use cases for closures.
In a relational database, the process of organizing data to minimize redundancy is known as ________.
- Normalization
- Denormalization
- Optimization
- Serialization
In a relational database, the process of organizing data to minimize redundancy is known as "Normalization." This technique helps in avoiding data anomalies and maintaining data integrity by breaking down tables into smaller, related tables.
To integrate ESLint with your editor, you can use an ESLint ________ for your specific editor.
- Extension
- Plugin
- Configuration
- Package
To integrate ESLint with your code editor, you can use an ESLint extension specifically designed for your editor. These extensions provide a user-friendly interface for running ESLint within your coding environment. While plugins and configurations are related to ESLint setup, they do not directly integrate with the editor. Packages, in this context, are not typically used for integrating ESLint with editors.
You are building an API using Express.js, and you want to ensure that the client receives meaningful error messages when something goes wrong. How would you structure your error-handling middleware to achieve this?
- Send status code 200 for all errors
- Use generic error messages for all errors
- Create custom error classes and send detailed error messages
- Log errors to the console only
To ensure that clients receive meaningful error messages, you should structure your error-handling middleware to create custom error classes and send detailed error messages. This allows you to provide specific information about the nature of the error, making it easier for clients to understand and handle errors gracefully. Sending generic error messages or using status code 200 for all errors would not provide meaningful information to clients. Logging errors to the console only is not sufficient for client communication.
To avoid cross-site scripting (XSS) attacks, EJS escapes any JavaScript code included within the ______ tags by default.
- <%= %>
- {{ }}
- {% %}
- ()()
In EJS, to avoid XSS attacks, JavaScript code is escaped by default when placed within <%= %> tags. This means that any code within these tags will be treated as plain text and not executed. The other options are not used for escaping JavaScript code in EJS.
Which npm script is automatically run when the npm publish command is executed?
- prepublish
- postpublish
- prepublishOnly
- prepare
The prepublishOnly script is automatically run when the npm publish command is executed. This script allows you to perform actions before the package is prepared for publication. It's commonly used for tasks like running tests or building production-ready code before publishing.
How does the lexical scoping mechanism work in JavaScript?
- It allows functions to access variables defined in their caller's scope.
- It restricts variables to the global scope only.
- It enforces strict mode in JavaScript.
- It determines the order of function execution.
Lexical scoping in JavaScript allows functions to access variables from their containing or parent scopes. This means that inner functions can access variables defined in outer functions, but not vice versa. The other options do not accurately describe lexical scoping.
You are developing a complex application where each module has several dependencies. How would you structure your tests in Mocha to ensure that each module is tested in isolation?
- Before each test, stub or mock the dependencies to isolate the module being tested.
- Use only integration tests to ensure dependencies are properly integrated.
- Test each module separately but don't worry about dependencies.
- Test modules with real dependencies to ensure accurate results.
To ensure isolation, you should stub or mock the dependencies of each module before each test in Mocha. This prevents external factors from affecting the test results. The other options do not promote isolation, which is crucial for unit testing.
In Node.js, the uncaughtExceptionMonitor event is triggered when an uncaughtException event occurs and there is no exception handler to handle it.
- error handler
- event listener
- exception catcher
- error catcher
Error Handling in Node.js
When creating a buffer in Node.js, if you do not specify an encoding type, the data will be treated as ______.
- binary
- text
- utf-8
- base64
If you don't specify an encoding type when creating a buffer in Node.js, the data will be treated as binary. This means that Node.js will not attempt to interpret the content as characters but will treat it as raw binary data.
Which statement is true regarding the order of executing imported and exporting modules?
- Exported modules are always executed before imported modules.
- Imported modules are executed first, followed by the execution of exported modules.
- The order of execution depends on the module loader and cannot be determined.
- Imported and exported modules are executed simultaneously.
In Node.js, when a module is imported, its code is executed immediately. Therefore, imported modules are executed first, and then the importing module's code continues to execute. This order ensures that the imported module's functionality is available to the importing module.
How can using Content Delivery Networks (CDNs) contribute to the performance optimization of web applications?
- A CDN improves web application performance by serving content from a centralized server.
- CDNs can execute JavaScript code more efficiently.
- CDNs reduce the need for encryption in web applications.
- CDNs automatically optimize database queries.
Content Delivery Networks (CDNs) contribute to web application performance optimization by caching and serving static content from edge servers located closer to the user. This reduces latency and offloads the main server, leading to faster load times. The other options are not accurate descriptions of CDN benefits.