In JS, each standalone file is its own separate program.

It may surprise you to consider separate .js files as separate JS programs. From the perspective of your usage of an application, it sure seems like one big program. That’s because the execution of the application allows these individual programs to cooperate and act as one program.

Since ES6, JS has also supported a module format in addition to the typical standalone JS program format. Modules are also file-based. If a file is loaded via module-loading mechanism such as an statement or a <script type=module> tag, all its code is treated as a single module.

Regardless of which code organization pattern (and loading mechanism) is used for a file (standalone or module), you should still think of each file as its own (mini) program, which may then cooperate with other (mini) programs to perform the functions of your overall application.