Which of the following is the correct way to declare an array in JavaScript?
- var myArray = [];
- array myArray = [];
- myArray = new Array();
- myArray = {}
The correct way to declare an array in JavaScript is by using square brackets []. So, var myArray = []; is the correct syntax. The other options are either not valid or used in different programming languages.
Which middleware is commonly used in Express.js to handle user authentication?
- express-auth
- passport
- jsonwebtoken
- authenticator
In Express.js, the commonly used middleware for handling user authentication is passport. Passport is a widely adopted authentication middleware that provides various authentication strategies for different authentication providers like local, Google, Facebook, and more. The other options are not standard authentication middleware for Express.js.
In JWT, what part of the token is responsible for holding the user's information?
- Payload
- Header
- Signature
- Claims
In JWT (JSON Web Tokens), the user's information is typically held in the Payload. The Payload contains claims, which are statements about an entity (typically, the user) and additional data. The Header contains metadata, and the Signature is used for verification.
What is the prototype of an object in JavaScript?
- __proto__
- prototype
- base
- parent
In JavaScript, the __proto__ property is a reference to the prototype object that an object inherits from. It is an internal property and can be accessed using object.__proto__. The prototype property, on the other hand, is a property of constructor functions and is used to define the prototype for objects created using that constructor. The other options are not commonly used for this purpose.
What can be the potential security risks if CORS is not properly implemented?
- Cross-Site Scripting (XSS) attacks
- Server crashes
- Slow page load times
- Improved website performance
If CORS is not properly implemented, it can lead to potential security risks such as Cross-Site Scripting (XSS) attacks. Without proper CORS configuration, malicious websites could make requests to your server from a user's browser, potentially leading to security vulnerabilities. The other options do not directly relate to CORS security risks.
How do closures impact memory usage in JavaScript, and how can memory leaks be prevented when using closures?
- Closures can increase memory usage as they retain access to their outer function's variables even after the outer function has completed execution. To prevent memory leaks, it's important to ensure that closures don't unintentionally keep references to objects or variables that are no longer needed. One common technique is to nullify references within the closure when they are no longer needed.
- Memory usage in JavaScript with closures can be a concern as closures retain references to their enclosing function's variables, preventing them from being garbage collected. To prevent memory leaks, developers should be diligent about managing references within closures, setting them to null when they are no longer needed.
- Closures in JavaScript can lead to increased memory usage since they capture variables from their parent scope. To prevent memory leaks, it's important to release references in closures explicitly, using techniques like setting variables to null.
- Closures in JavaScript can lead to increased memory usage as they retain references to their enclosing function's variables. To prevent memory leaks, developers should be cautious about what they capture in closures and consider using a memory profiling tool to identify and resolve issues.
Closures and Memory Management
When creating a custom readable stream in Node.js, implementing the '______' method is essential to supply the stream with data chunks.
- push
- write
- read
- pipe
When creating a custom readable stream in Node.js, implementing the 'read' method is essential to supply the stream with data chunks. This method is invoked by the stream consumer to request data. It should be implemented to push data into the stream using the 'push' method or emit 'data' events.
The ______ property of the request object in the http module contains the HTTP method of the request.
- method
- type
- httpMethod
The method property of the request object in the http module contains the HTTP method of the request. This property allows you to determine whether the request is a GET, POST, PUT, DELETE, or another HTTP method, which is important for routing and handling requests correctly.
What considerations should be taken into account while implementing Role-Based Access Control (RBAC) in Express.js applications?
- Properly define roles and their permissions, enforce access control at the route level, and perform input validation.
- RBAC should only be implemented on the client side to avoid server overhead.
- RBAC implementation should allow any user to access any resource without restrictions.
- Roles should be hardcoded in the application without the ability to modify them.
When implementing RBAC in Express.js, it's crucial to define roles and their associated permissions, enforce access control at the route level, and perform input validation to prevent unauthorized access. The other options are incorrect as they neglect key considerations for RBAC implementation.
How does the Event Loop interact with the Worker Threads in Node.js for handling CPU-intensive tasks?
- The Event Loop directly executes CPU-intensive tasks within its own thread.
- The Event Loop manages CPU-intensive tasks by offloading them to separate Worker Threads.
- The Event Loop blocks until CPU-intensive tasks are completed.
- CPU-intensive tasks are not supported in Node.js.
The Event Loop in Node.js can interact with Worker Threads to handle CPU-intensive tasks. These Worker Threads run in the background, separate from the Event Loop, and can be used to prevent blocking the main thread when performing CPU-intensive operations, such as complex calculations.