In the fs module of Node.js, synchronous methods are identified by the Sync suffix. For example, fs.readFileSync is a synchronous method for reading files, whereas asynchronous methods do not have this suffix.

Jest is a popular testing framework commonly used for writing tests in Node.js applications. It provides a comprehensive toolset for testing and is known for its simplicity and speed.

The commonly used configuration file for ESLint is .eslintrc.json. This file allows you to specify ESLint rules, plugins, and other configuration options for your project.

The GET HTTP method is used for reading data in CRUD (Create, Read, Update, Delete) operations. It retrieves data from the server without making any modifications.

The for loop structure in JavaScript is used when you want to execute a block of code a specific number of times, as it allows you to set the initialization, condition, and incrementation all in one place. While the other options (while, do-while, if) are used for different purposes, they don't inherently control the number of iterations like the for loop.

The default behavior of Express when an error occurs in a middleware is to send a 500 Internal Server Error response. This ensures that the client receives an appropriate error response when something goes wrong in the middleware chain. The other options describe different behaviors that do not occur by default.

The rest operator (...) is used in function parameters to collect all remaining arguments into an array. In the example function myFunction(a, b, ...rest), the ...rest collects any additional arguments passed to the function into an array named rest.

To make the properties of an object immutable in JavaScript, you can use the Object.freeze() method. This method prevents any changes to the object's properties, making them read-only. The other options, Object.preventExtensions() and Object.seal(), allow some level of modification but not full immutability, and Object.makeImmutable() is not a valid method in JavaScript.

When creating a multidimensional array in JavaScript, each element of the main array is a reference to another array or value. This allows for the creation of nested arrays. Changes made to the referenced arrays will affect the main array.

In JavaScript, you can use a while loop to execute a block of code repeatedly as long as a specified condition is true. The for loop is used for iterating over a sequence, and if and switch statements are conditional constructs, not loops.