Custom module not being recognized in app.js

Problem Overview

When defining a custom module in AngularJS, you might encounter an error stating that the module is not recognized in app.js. The error could look like:

Error: [$injector:modulerr] Failed to instantiate module myCustomModule due to:
Error: [$injector:nomod] Module 'myCustomModule' is not available!

This issue arises when:

The module is not defined correctly.
The module is not included as a dependency in app.js.
There is a typo in the module name.
The module loads after app.js executes.

1. Correct Way to Define a Custom Module

Step 1: Define the Custom Module
Create a separate JavaScript file for your module, for example, customModule.js.

angular.module('myCustomModule', [])
  .service('customService', function() {
      this.sayHello = function() {
          return 'Hello from myCustomModule!';
      };
  });

Step 2: Inject the Custom Module into app.js
Modify app.js to include 'myCustomModule' as a dependency.

angular.module('myApp', ['myCustomModule'])
  .controller('MainController', function($scope, customService) {
      $scope.message = customService.sayHello();
  });

Why This Works?

['myCustomModule'] ensures AngularJS loads the module before using it.
customService is now available in MainController.

2. Common Issues and Fixes

Issue 1: The Module is Not Loaded Before `app.js`

Problem:
If app.js executes before customModule.js, AngularJS won’t recognize the module.

Check the Order in index.html

<script src="angular.min.js"></script>
<script src="customModule.js"></script> <!--  Load first -->
<script src="app.js"></script>          <!--  Load after -->

Fix:

Ensure customModule.js loads before app.js.
If modules load dynamically, use AngularJS’s lazy loading.

Issue 2: Typo in Module Name

Problem:
A small typo in app.js can break module recognition.

Incorrect (typo in module name):

angular.module('myApp', ['myCustomModul']) //  'myCustomModul' is incorrect

Fix:
Check the module name in customModule.js and app.js—they must match exactly.

Issue 3: Module is Defined Multiple Times (`[$injector:modulerr]`)

Problem:
If you mistakenly redefine a module instead of reusing it, you might see:

[$injector:modulerr] Failed to instantiate module

Incorrect (Redefining the module):

// First definition (correct)
angular.module('myCustomModule', []);

// Second definition (incorrect)
angular.module('myCustomModule', []) //  This erases the previous definition
  .service('anotherService', function() {});

Fix:
Use angular.module('moduleName') without brackets when reusing an existing module.

angular.module('myCustomModule')
  .service('anotherService', function() {}); //  Correct

Issue 4: Circular Dependency (`[$injector:cdep]`)

Problem:
If myCustomModule depends on myApp, and myApp depends on myCustomModule, you get a circular dependency.

Incorrect: Circular Dependency

angular.module('myCustomModule', ['myApp']); //  Depends on myApp
angular.module('myApp', ['myCustomModule']); //  myApp also depends on myCustomModule

Fix:
Remove one of the dependencies to break the loop.

Issue 5: Module Not Registered Due to Script Errors

Problem:
Syntax errors prevent module registration, causing AngularJS to not recognize it.

Check Console for Errors Open Chrome DevTools → Console and look for syntax errors.

Incorrect: Missing Brackets (() in function):

angular.module('myCustomModule')
  .service('customService', function {
      this.sayHello = function() { return 'Hello'; } // ❌ Syntax error (missing `()`)
  });

Fix:

angular.module('myCustomModule')
  .service('customService', function() { //  Correct function syntax
      this.sayHello = function() { return 'Hello'; };
  });

3. Debugging Module Recognition Issues

1. Verify Module Exists Using DevTools

Run this in Chrome DevTools Console:

angular.module('myCustomModule');

If it prints the module definition, the module exists.
If you see Error: [$injector:nomod], the module was not registered.

2. Log All AngularJS Modules

To check if myCustomModule is loaded:

angular.module('myApp').requires

If it outputs ['myCustomModule'], the module is included.

3. Force AngularJS to Recompile Modules

If the module is dynamically loaded:

angular.bootstrap(document, ['myApp']);

Forces AngularJS to recompile modules.
Useful if app.js loads before the module.

4. Summary

Why Is a Custom Module Not Recognized?

app.js executes before customModule.js.
Module name typo in app.js.
Redefining the module instead of reusing it.
Circular dependency between modules.
Syntax errors prevent module registration.