How can you remove a listener from an event using the Events module in Node.js?
- event.removeListener(event, listener)
- event.remove(listener)
- event.off(event, listener)
- listener.remove(event)
To remove a listener from an event using the Events module in Node.js, you should use the event.removeListener(event, listener) method. This method takes the event name and the listener function as arguments and removes the specified listener from the event. The other options are not valid methods for removing listeners.
You are integrating ESLint into a legacy project. How would you approach linting the existing codebase without disrupting the development workflow?
- Lint the entire codebase in one go and fix all issues immediately.
- Gradually introduce ESLint, starting with new code and addressing legacy code issues incrementally.
- Disable ESLint for the legacy code and only apply it to new code.
- Ignore linting in legacy projects as it can't be easily integrated.
To avoid disruption, it's best to gradually introduce ESLint. Start by applying it to new code and address legacy code issues incrementally. Linting the entire codebase at once might be overwhelming and disruptive. Disabling ESLint for legacy code or ignoring it is not a recommended approach for maintaining code quality.
You are developing an application with multiple user roles, and each role has different levels of access to resources. How would you securely implement role-based access control to prevent unauthorized access?
- Use JSON Web Tokens (JWT) to manage user sessions and roles.
- Implement access control lists (ACLs) in your application.
- Check the user's role in the frontend to determine access.
- Rely solely on server-side sessions to control access.
Option (1) is correct. Using JWTs for session management and roles is a secure approach as they are self-contained and can be verified without relying on server-side sessions. Options (2) and (4) are less secure and may lead to vulnerabilities. Option (3) is incorrect as access control should be enforced on the server.
Which of the following ESLint rules enforces consistent indentation in your code?
- no-console
- indent
- semi
- no-unused-vars
The indent rule in ESLint enforces consistent indentation in your code. It helps ensure that your code is properly formatted and readable by specifying the expected indentation style. The other options are for different rules, such as preventing the use of console, enforcing semicolons, or catching unused variables.
What is the first argument typically passed to a callback function in Node.js to handle errors?
- result
- data
- error
- callback
The first argument typically passed to a callback function in Node.js to handle errors is error. This argument holds information about any errors that may have occurred during the asynchronous operation. The other options (result, data, and callback) are used for different purposes in callback functions.
When the Event Loop encounters an asynchronous task, it offloads it to the ________ and continues to execute subsequent tasks.
- Callback Queue
- Worker Thread
- Event Emitter
- Main Memory
When the Event Loop encounters an asynchronous task, it offloads it to the Callback Queue and continues to execute subsequent tasks. These tasks are then processed from the Callback Queue when the main thread is available.
What is the significance of the call(), apply(), and bind() methods in JavaScript functions?
- They are used for declaring global variables.
- They enable asynchronous execution of functions.
- They manipulate the DOM.
- They facilitate the manipulation of function context and parameter passing.
call(), apply(), and bind() are methods in JavaScript used to manipulate the context in which a function is executed and to pass arguments to functions. They are commonly used in scenarios like setting the value of 'this' in a function and passing arguments dynamically. None of the other options correctly describe their purpose.
You are developing a real-time analytics dashboard that requires aggregation of data from multiple tables. How can you optimize the queries to ensure minimum latency in displaying the results?
- Use caching mechanisms
- Opt for synchronous queries to ensure real-time data
- Optimize database indexes
- Use a single table to store all data
To ensure minimum latency in a real-time analytics dashboard, using caching mechanisms is essential. Caching can store frequently used aggregated data and serve it quickly, reducing the need for complex queries. Options B and D do not align with best practices for real-time analytics. Option C is a good practice but not as directly related to real-time performance as caching.
In Express.js, to catch errors from a promise within a route, the next function should be called with the ______ as an argument.
- error
- promise
- err
- next
In Express.js, to catch errors from a promise within a route, the next function should be called with the err as an argument. This allows Express.js to recognize it as an error-handling middleware. Passing error, promise, or next itself would not trigger the error handling mechanism in Express.js.
In JavaScript, objects created using object literal syntax are instances of ______.
- Object
- Function
- Prototype
- Class
In JavaScript, objects created using object literal syntax are instances of the Object constructor. This means they inherit properties and methods from the Object prototype.