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Argument Maincontroller Is Not A Function Got Undefined In Angularjs Duplicate

If you're building a web application using AngularJS and ran into the error "Argument 'MainController' is not a function, got undefined," you're in the right place. This common issue can be frustrating, but fear not! We'll guide you through understanding and resolving this error step by step.

### Understanding the Error:

When you encounter the "Argument 'MainController' is not a function, got undefined" error in AngularJS, it usually means that AngularJS is unable to find or recognize the controller you are referencing in your code. This can happen due to various reasons, such as incorrect controller registration, naming mismatches, or script loading order issues.

### Solution Steps:

#### 1. Check Controller Registration:
The first thing to do is to verify the registration of your `MainController` in the AngularJS application module. Check that the controller is properly defined within the module and that its name matches the one you are using in your HTML markup.

Javascript

angular.module('myApp', [])
  .controller('MainController', function($scope) {
    // Controller logic here
  });

#### 2. Script Loading Order:
Ensure that your scripts are loaded in the correct order. If the script defining the `MainController` is loaded after the script where `MainController` is referenced, AngularJS won't be able to find the controller. Make sure the controller script is loaded before it's referenced in your HTML.

#### 3. Debugging in the Browser:
Use the browser's developer tools to inspect the console for any other error messages that might give you additional insights into the problem. Check for any typos or syntax errors in your code that could be causing the issue.

#### 4. Double-Check Module Dependency:
Verify that the module where `MainController` is defined is included as a dependency in your main application module.

Javascript

angular.module('myApp', ['mainModule'])
  .controller('MainController', function($scope) {
    // Controller logic here
  });

angular.module('mainModule', []);

### Conclusion:
By following these steps and understanding the nature of the error "Argument 'MainController' is not a function, got undefined," you should be able to diagnose and resolve the issue in your AngularJS application. Remember to double-check your code for any naming inconsistencies, script loading problems, or module dependencies that might be causing the error.

Don't let this error halt your progress – tackle it head-on with these troubleshooting tips and get your AngularJS application back on track!

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