The primary use of Streams in Node.js is for handling data in a streaming fashion, especially for reading and writing data efficiently. They are commonly used for handling HTTP requests and responses, file I/O, and more, where data can be processed in smaller chunks without loading the entire dataset into memory.

The output of the code snippet is true. In JavaScript, the == operator performs type coercion, so it converts the string '1' to a number before comparing, and 1 is equal to 1.

Custom middleware is implemented in Express.js when you have specific application logic that cannot be handled by built-in middleware. Common scenarios include authentication, request logging, data validation, and handling application-specific errors. Built-in middleware covers common use cases, but custom middleware allows you to tailor the middleware pipeline to your application's unique needs.

To destructure nested properties in JavaScript objects, you should use the syntax in Option 2. It allows you to access nested properties within myObject. The other options either contain incorrect syntax or won't work for this purpose.

When creating a mock object in unit testing, you typically expect its methods to behave in a simplified or controlled manner. Mock objects are used to simulate the behavior of real objects for testing purposes, so their methods should provide predictable responses that help you test specific scenarios. Options (1) and (4) are not typical expectations for mock methods. Option (2) would render the mock object useless for testing.

To copy a file from one location to another using the fs module, you can use the fs.copyFile() method. This method allows you to copy the contents of one file to another location. The other options (fs.moveFile(), fs.rename(), and fs.copy()) serve different purposes in file manipulation but are not specifically for copying a file to another location.

The correct script in the package.json file that runs after the package is uninstalled but before it is unpublished is the postuninstall script. This script is commonly used for cleanup tasks or notifications. The other options are not standard scripts for this purpose.

The continue statement in a loop is used to skip the remaining part of the current iteration (loop body) and move on to the next iteration. It helps control the flow of a loop.

The scripts section in package.json is used to define custom scripts for various build tasks, test scripts, and more. It aids in automating and enhancing the build process by providing a central place to manage these tasks. Options 1 and 2 are not related to the scripts section, and option 4 is not a recommended approach.

The Buffer class in Node.js is extremely useful when dealing with binary data. It provides methods for efficiently working with raw binary data, making it suitable for tasks such as reading and writing files, working with network protocols, and handling binary data in memory.

Destructuring an array in JavaScript is done using square brackets []. The correct syntax is let [x, y] = [1, 2];. The other options are either for object destructuring or use incorrect syntax.

Unit Testing focuses on verifying the functionality of individual components (or units) in isolation. It helps ensure that each component works correctly on its own.