Error: Unexpected value 'undefined' imported by the module

Question

For anyone facing this same error, my situation was that I have double commas in the imports section

imports: [
      BrowserModule,
      HttpModule,
      FormsModule,
      RouterModule.forRoot(appRoutes), , // <-- this was the error
      // .... 
],

Make sure the modules don't import each other. So, there shouldn't be

In Module A: imports[ModuleB]

In Module B: imports[ModuleA]

This can be caused by multiple scenarios like

1. Missing commas

imports: [
    BrowserModule
   ,routing <= Missing Comma
   ,FeatureComponentsModule
  ],

2. Double Commas

imports: [
    BrowserModule, 
   ,routing <=Double Comma
   ,FeatureComponentsModule
  ],

3. Exporting Nothing from the Module
4. Syntax errors
5. Typo Errors
6. Semicolons inside Objects, Arrays
7. Incorrect import Statements

I had the same problem. In my case, the reason is an extra comma.

None of the above solutions worked for me, but simply stopping and running "ng serve" again.