How can Typescript ensure that all declarations can be seen in all files?

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Typescript ensures that all declarations can be seen in all files by using module systems. Modules are separate files that export and import declarations to and from each other. When a Typescript project is compiled, it creates a single output file that includes all of the individual module files. This allows all of the declarations to be visible to all of the files within the project. Additionally, Typescript has a feature called ambient declarations, which allow declarations to be made globally across the entire project, making them visible from any file without needing to import or export them explicitly.