Simulate a private scope — practice exercise

What you'll be asked to do

1. 1.Simulate a private scopeexercise · easy · 10 min

   Keep a value private and expose only a method that uses it.

   Passes when: #out should show 10.

2. 2.Hide an unexported nameexercise · easy · 10 min · practice plan

   Show that a private helper cannot be reached from outside.

   Passes when: #out should show hidden.

3. 3.Run a module onceexercise · easy · 10 min · practice plan

   Show that importing the same module twice shares one result.

   Passes when: #out should show same object.

4. 4.Keep two modules separateexercise · easy · 10 min · practice plan

   Show that two simulated modules do not share their private state.

   Passes when: #out should show 5 and 10.

5. 5.Show modules run in strict modeexercise · medium · 10 min · practice plan

   Catch the error an undeclared assignment throws in strict mode.

   Passes when: #out should show ReferenceError.

6. 6.Fix the private value exposedbug fix · easy · 8 min

   The internal value should not be part of the returned object.

   Passes when: #out should show hidden.

7. 7.Fix the shared global variablebug fix · easy · 8 min · practice plan

   Two plain scripts sharing one scope overwrite each other's variable.

   Passes when: #out should show 5.

8. 8.Fix the modules sharing statebug fix · easy · 8 min · practice plan

   Each module should keep its own private total instead of a variable both can see.

   Passes when: #out should show 5 and 10.

9. 9.Fix the module re-run unnecessarilybug fix · easy · 8 min · practice plan

   The same loaded module should be reused, not rebuilt.

   Passes when: #out should show 1.

10. 10.Fix strict mode never appliedbug fix · easy · 8 min · practice plan

    Without strict mode, an undeclared assignment silently creates a global instead of throwing.

    Passes when: #out should show ReferenceError.

Between them these tasks cover Module scope, Isolation and Caching.

Looking for a different chapter? See every practice set, or switch to the interview theory questions.