How can the design of the Event Loop and Non-Blocking I/O lead to potential pitfalls in application behavior, such as callback hell or race conditions?
- The design ensures that such pitfalls are impossible in Node.js applications.
- Callback hell and race conditions are unrelated to the Event Loop and Non-Blocking I/O.
- Callback hell can occur due to deeply nested asynchronous callbacks, making code hard to read and maintain. Race conditions can happen when multiple asynchronous operations access shared resources without proper synchronization.
- Non-Blocking I/O eliminates all potential issues.
The design of the Event Loop and Non-Blocking I/O in Node.js can lead to challenges in application development. Callback hell can occur when developers create deeply nested asynchronous callbacks, making code hard to read and maintain. Race conditions can arise when multiple asynchronous operations access shared resources without proper synchronization, potentially leading to unexpected behavior. Understanding these pitfalls is crucial for writing efficient Node.js applications.
How can you create a private variable inside a JavaScript function?
- Use the 'private' keyword before declaring a variable.
- Declare the variable inside a function using 'var'.
- Use a function closure to encapsulate the variable within the function's scope.
- Use 'let' or 'const' to declare the variable inside a function.
To create a private variable in JavaScript, you can use a function closure. By defining a variable inside a function and not exposing it outside the function's scope, you can achieve encapsulation and create a private variable that is inaccessible from outside the function.
In JavaScript, the Symbol data type was introduced in ________.
- ECMAScript 2015 (ES6)
- JavaScript 1.5
- Node.js v10
- ESNext
The Symbol data type was introduced in ECMAScript 2015 (ES6). It allows you to create unique and immutable values that can be used as object property keys.
In Express.js, middleware functions have access to the request object, the response object, and the ______ function.
- next()
- send()
- app()
- router()
In Express.js, middleware functions have access to the request object (req), the response object (res), and a callback function commonly named next(). The next() function is used to pass control to the next middleware function in the chain.
Which of the following is the primary goal of input sanitization?
- Enhancing user experience.
- Ensuring data accuracy.
- Preventing cross-site scripting (XSS) attacks.
- Optimizing database performance.
The primary goal of input sanitization is to prevent cross-site scripting (XSS) attacks. It involves removing or encoding potentially dangerous characters from user input to ensure that it cannot be executed as script on a web page, thus enhancing web security.
Which of the following is an example of an Object Document Mapper (ODM) for MongoDB in Node.js?
- Mongoose
- Sequelize
- Knex
- TypeORM
Mongoose is a popular Object Document Mapper (ODM) for MongoDB in Node.js. It provides a structured way to interact with MongoDB, allowing developers to define schemas and models for their data. The other options, Sequelize, Knex, and TypeORM, are primarily used with relational databases and are not ODMs for MongoDB.
When dealing with CORS, the Access-Control-Allow-Credentials header should be set to true to allow ________ to be included in the request.
- cookies
- headers
- authentication
- origins
When dealing with CORS, the Access-Control-Allow-Credentials header should be set to true to allow cookies to be included in cross-origin requests. This is necessary when you want to make authenticated requests across origins.
You are developing a system with stringent data integrity requirements. How would you design the schema to enforce data integrity constraints and handle violations effectively?
- Use database triggers to enforce constraints.
- Implement application-level validation only.
- Apply foreign key constraints to maintain data relationships.
- Rely solely on user input validation.
Option (1) is a valid approach using database triggers to enforce constraints. Option (2) shouldn't be the sole method, as application-level validation can be bypassed. Option (3) is essential, especially for maintaining data relationships. Option (4) is not sufficient for ensuring data integrity on its own.
How can developers handle multiple callback functions to avoid "Callback Hell" in Node.js?
- Nest callbacks within each other for better organization.
- Use async/await to write asynchronous code more sequentially.
- Avoid callbacks altogether and use Promises exclusively.
- Increase the event loop's capacity for handling callbacks.
To avoid "Callback Hell" in Node.js, developers can use async/await, which allows them to write asynchronous code in a more sequential and readable manner. This approach reduces the nesting of callbacks and makes the code easier to maintain.
How can you handle error responses in Express for cleaner error reporting?
- Using the throw statement
- Using the try...catch block
- Implementing custom error handling middleware
- Ignoring errors for cleaner logs
To handle error responses in Express for cleaner error reporting, you can implement custom error handling middleware. This middleware can catch errors and provide a standardized way to handle and respond to them, improving error reporting and debugging.