Simulate deferred loading — practice exercise

What you'll be asked to do

1. 1.Simulate deferred loadingexercise · easy · 10 min

   Show that reading an element only works once the page is ready.

   Passes when: #out should show found it.

2. 2.Show it runs onceexercise · easy · 10 min · practice plan

   Simulate a module loaded twice sharing one execution.

   Passes when: #out should show 1.

3. 3.Report the CORS requirementexercise · easy · 10 min · practice plan

   Report that a cross-origin module needs a CORS-friendly response.

   Passes when: #out should show needs CORS.

4. 4.Report the file protocol limitexercise · easy · 10 min · practice plan

   Report that module scripts need a real server.

   Passes when: #out should show needs a server.

5. 5.Simulate nomodule fallbackexercise · medium · 10 min · practice plan

   Report which script a module-aware browser runs.

   Passes when: #out should show module script.

6. 6.Fix the element read before it existsbug fix · easy · 8 min

   Reading before the page is ready gives nothing.

   Passes when: #out should show found it.

7. 7.Fix the module counted as loaded twicebug fix · easy · 8 min · practice plan

   A module included twice should still only run once.

   Passes when: #out should show 1.

8. 8.Fix CORS assumed to always allowbug fix · easy · 8 min · practice plan

   A cross-origin module without CORS headers should be blocked.

   Passes when: #out should show needs CORS.

9. 9.Fix file:// assumed to workbug fix · easy · 8 min · practice plan

   Module scripts generally need a real server protocol.

   Passes when: #out should show needs a server.

10. 10.Fix nomodule chosen for a supporting browserbug fix · easy · 8 min · practice plan

    A module-aware browser should run the module script, not the fallback.

    Passes when: #out should show module script.

Between them these tasks cover type=module, Deferred loading and Single execution.

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