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.

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.

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.

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.

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.

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.

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.

When using npm deprecate, the correct option is externally. This means that a deprecation warning message will be displayed to any developers installing the package from outside the project.

JavaScript performs implicit data type conversion, also known as type coercion, when operators or functions are used with values of different data types. This can lead to unexpected behavior, so it's important to understand how type coercion works in JavaScript.

Content Security Policy (CSP) helps prevent Cross-Site Scripting (XSS) attacks by defining rules for resource loading and script execution in web applications. It can restrict the sources from which scripts can be executed, mitigating the risk of malicious script injection. However, CSP has limitations, such as its inability to prevent all forms of XSS attacks, the need for careful configuration, and potential compatibility issues with legacy code.

In Express.js, you can use the app.get('/route', callback) method to match routes with a specific pattern. The get method is used to handle HTTP GET requests and is often used to define routes with specific patterns. The other options do not represent the standard way to define route patterns in Express.js.

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.