What will happen if you declare variables in module scope without using var, let, or const?

When you declare variables in module scope without using any defined keywords like var, let, or const, those variables will inadvertently become global variables accessible throughout the entire application. This behavior stems from the fact that JavaScript has a specific scoping mechanism. In non-strict mode, variables assigned without declaration keywords are added to the global object (window in the browser or global in Node.js).

This feature can lead to unintended consequences, such as variable name collisions and difficulties in debugging due to global namespaces being polluted with undeclared variables. This emphasizes the importance of using proper declaration keywords to ensure that variable scope is maintained as intended, either globally or locally.

In strict mode, however, assigning a variable without a declaration keyword would throw an error, highlighting how strict mode provides more safety in variable declarations. The other answer choices do not accurately describe this behavior, as undefined variables refer to uninitialized variables that have been declared, and scoped variables are limited to their declared environment, which is not the case here.