In semantic versioning (SemVer), the 'major' number represents significant changes that are not backwards-compatible. This means that if the 'major' version number increases, it indicates that there have been substantial changes in the software that may break compatibility with previous versions.

When you use the spread operator on a string in JavaScript, it splits the string into an array of individual characters. So, the correct result is an array of characters as shown in Option 1. The other options are not the expected outcome for the spread operator on a string.

In Jest, the 'expect' function is primarily used for making assertions in your test cases. It allows you to check whether the actual value matches the expected value. Assertions are crucial in determining whether your code behaves as intended and whether it passes the test.

The primary purpose of using modules in JavaScript is code organization and encapsulation. Modules help break down large programs into smaller, manageable pieces of code, making it easier to maintain and collaborate on projects. While modules can have other benefits, such as enhancing performance, their main role is to structure and organize code.

To prevent a specific package from being updated when running npm update, you can edit your project's package.json file and specify the exact version of the package you want. This ensures that the package remains at the specified version. Using "npm lock" is not a standard command, and running npm update --no-save will update the package.json file if used. Deleting and reinstalling the package is not a recommended approach as it can disrupt your project.

In Node.js, the commonly used package to connect to a MySQL database is mysql. This package provides a straightforward way to interact with MySQL databases, allowing you to establish connections and perform database operations. The other options are not standard packages for MySQL database connections.

The global object in a Node.js module is available only within the module where it is declared. It is not shared across all modules, and each module has its own isolated scope. The other options do not accurately describe the behavior of the Node.js global object.

Static imports are used at compile time and load modules synchronously, while dynamic imports are used at runtime and load modules asynchronously. Dynamic imports return a promise that resolves to the module.

For optimizing complex queries involving multiple JOIN operations, one can use "Subqueries" to break them into simpler, more manageable queries. Subqueries allow you to retrieve intermediate results that can be used in the main query.

In Express.js, middlewares are executed in the order they are defined. The order matters because each middleware can modify the request or response objects and pass them on to the next middleware.