Hey there! That [$injector:modulerr] error is one of the most common gotchas in AngularJS, but we can work through this together. Let’s break down the most likely causes and fixes to get your app back on track:

Common Causes & Troubleshooting Steps #

• Module Dependency Typo or Missing Dependency
  This is the #1 culprit. Double-check:

  • Your main module declaration (like angular.module('myApp', ['ngRoute', 'customModule'])) has correctly spelled dependency names—even a single wrong letter or capitalization will break things.
  • All dependent module files are included in your HTML, and in the right order (Angular core first, then third-party modules, then your custom modules, then your main app script).

• Incorrect Script Loading Order
  AngularJS needs to be loaded before any of your app’s code. Make sure your HTML script tags follow this sequence:

  <script src="angular.js"></script>
  <script src="angular-route.js"></script> <!-- Any third-party dependencies -->
  <script src="my-custom-module.js"></script>
  <script src="my-app.js"></script>
  

  Also, check the Network tab in your browser’s dev tools to confirm none of these scripts are throwing 404 errors.

• Minification-Safe Injection Issues
  If you’re minifying your code (or plan to), plain function parameter injection will break—minifiers rename variables, which Angular can’t resolve. Fix this by using one of two patterns:
  Array-style injection:

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

  Or the $inject property:

  function MyCtrl($scope, $http) { /* ... */ }
  MyCtrl.$inject = ['$scope', '$http'];
  angular.module('myApp').controller('MyCtrl', MyCtrl);
  

• Duplicate Module Definition
  Remember: angular.module('myApp', []) (with the dependency array) creates a new module every time you call it. If you accidentally use this syntax more than once, you’ll overwrite your module. Use angular.module('myApp') (without the second parameter) to retrieve an existing module.

Pro Tip #

Open your browser’s DevTools Console and look for the nested error message under [$injector:modulerr]—it’ll usually give you a more specific clue, like [$injector:nomod] (module doesn’t exist) or [$injector:unpr] (unknown provider), which narrows down the problem instantly.

内容的提问来源于stack exchange，提问作者J. Moura