How it works...

The * syntax seen on the first two lines of index.js imports all the exported members under the same object. This means that the name, COUNT_DOWN_DURATION, and launch members of falcon-heavey.js are all attached to the falconHeavy variable. Likewise, for the saturn-v.js modules and the saturnV variable. So, when falconHeavy and saturnV are exported on line 4, those exported names now contain all the exported members of their respective modules.

This provides a single point where another module (main.js in this case) can import those members. The pattern has three advantages. It is simple; there is only one file to import members from, rather than many. It is consistent, because all packages can use an index module to expose members of multiple modules. It is more flexible; members of some modules can be used throughout a package and not be exported by the index module.