---
name: angular-migration
description: "Master AngularJS to Angular migration, including hybrid apps, component conversion, dependency injection changes, and routing migration."
risk: critical
source: community
date_added: "2026-02-27"
---
## Supporting material availability

This catalog copy contains the inline guidance below, but does not include the following supporting paths. They are external prerequisites, not bundled files:

- `<support-root>/references/hybrid-mode.md`
- `<support-root>/references/component-migration.md`
- `<support-root>/references/dependency-injection.md`
- `<support-root>/references/routing.md`
- `<support-root>/assets/hybrid-bootstrap.ts`
- `<support-root>/assets/migration-timeline.md`
- `<support-root>/scripts/analyze-angular-app.sh`

Ask for the original supporting material or an existing installation before using a step that depends on these paths; this catalog does not identify a verified download source for them. Resolve each path relative to that installation, inspect its contents, and verify any applicable license and execution prerequisites. Do not run a command or claim a referenced procedure was followed until its required file exists. Do not fabricate the missing scripts or treat an unrelated file with the same name as equivalent. Independent steps fully documented here can proceed within the user’s authorized scope; report any dependent step as unavailable.


# Angular Migration

Master AngularJS to Angular migration, including hybrid apps, component conversion, dependency injection changes, and routing migration.

## Use this skill when

- Migrating AngularJS (1.x) applications to Angular (2+)
- Running hybrid AngularJS/Angular applications
- Converting directives to components
- Modernizing dependency injection
- Migrating routing systems
- Updating to latest Angular versions
- Implementing Angular best practices

## Do not use this skill when

- You are not migrating from AngularJS to Angular
- The app is already on a modern Angular version
- You need only a small UI fix without framework changes

## Instructions

1. Assess the AngularJS codebase, dependencies, and migration risks.
2. Choose a migration strategy (hybrid vs rewrite) and define milestones.
3. Set up ngUpgrade and migrate modules, components, and routing.
4. Validate with tests and plan a safe cutover.

## Safety

- Avoid big-bang cutovers without rollback and staging validation.
- Keep hybrid compatibility testing during incremental migration.

## Migration Strategies

### 1. Big Bang (Complete Rewrite)
- Rewrite entire app in Angular
- Parallel development
- Switch over at once
- **Best for:** Small apps, green field projects

### 2. Incremental (Hybrid Approach)
- Run AngularJS and Angular side-by-side
- Migrate feature by feature
- ngUpgrade for interop
- **Best for:** Large apps, continuous delivery

### 3. Vertical Slice
- Migrate one feature completely
- New features in Angular, maintain old in AngularJS
- Gradually replace
- **Best for:** Medium apps, distinct features

## Hybrid App Setup

```typescript
// main.ts - Bootstrap hybrid app
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { UpgradeModule } from '@angular/upgrade/static';
import { AppModule } from './app/app.module';

platformBrowserDynamic()
  .bootstrapModule(AppModule)
  .then(platformRef => {
    const upgrade = platformRef.injector.get(UpgradeModule);
    // Bootstrap AngularJS
    upgrade.bootstrap(document.body, ['myAngularJSApp'], { strictDi: true });
  });
```

```typescript
// app.module.ts
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { UpgradeModule } from '@angular/upgrade/static';

@NgModule({
  imports: [
    BrowserModule,
    UpgradeModule
  ]
})
export class AppModule {
  constructor(private upgrade: UpgradeModule) {}

  ngDoBootstrap() {
    // Bootstrapped manually in main.ts
  }
}
```

## Component Migration

### AngularJS Controller → Angular Component
```javascript
// Before: AngularJS controller
angular.module('myApp').controller('UserController', function($scope, UserService) {
  $scope.user = {};

  $scope.loadUser = function(id) {
    UserService.getUser(id).then(function(user) {
      $scope.user = user;
    });
  };

  $scope.saveUser = function() {
    UserService.saveUser($scope.user);
  };
});
```

```typescript
// After: Angular component
import { Component, OnInit } from '@angular/core';
import { UserService } from './user.service';

@Component({
  selector: 'app-user',
  template: `
    <div>
      <h2>{{ user.name }}</h2>
      <button (click)="saveUser()">Save</button>
    </div>
  `
})
export class UserComponent implements OnInit {
  user: any = {};

  constructor(private userService: UserService) {}

  ngOnInit() {
    this.loadUser(1);
  }

  loadUser(id: number) {
    this.userService.getUser(id).subscribe(user => {
      this.user = user;
    });
  }

  saveUser() {
    this.userService.saveUser(this.user);
  }
}
```

### AngularJS Directive → Angular Component
```javascript
// Before: AngularJS directive
angular.module('myApp').directive('userCard', function() {
  return {
    restrict: 'E',
    scope: {
      user: '=',
      onDelete: '&'
    },
    template: `
      <div class="card">
        <h3>{{ user.name }}</h3>
        <button ng-click="onDelete()">Delete</button>
      </div>
    `
  };
});
```

```typescript
// After: Angular component
import { Component, Input, Output, EventEmitter } from '@angular/core';

@Component({
  selector: 'app-user-card',
  template: `
    <div class="card">
      <h3>{{ user.name }}</h3>
      <button (click)="delete.emit()">Delete</button>
    </div>
  `
})
export class UserCardComponent {
  @Input() user: any;
  @Output() delete = new EventEmitter<void>();
}

// Usage: <app-user-card [user]="user" (delete)="handleDelete()"></app-user-card>
```

## Service Migration

```javascript
// Before: AngularJS service
angular.module('myApp').factory('UserService', function($http) {
  return {
    getUser: function(id) {
      return $http.get('/api/users/' + id);
    },
    saveUser: function(user) {
      return $http.post('/api/users', user);
    }
  };
});
```

```typescript
// After: Angular service
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class UserService {
  constructor(private http: HttpClient) {}

  getUser(id: number): Observable<any> {
    return this.http.get(`/api/users/${id}`);
  }

  saveUser(user: any): Observable<any> {
    return this.http.post('/api/users', user);
  }
}
```

## Dependency Injection Changes

### Downgrading Angular → AngularJS
```typescript
// Angular service
import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class NewService {
  getData() {
    return 'data from Angular';
  }
}

// Make available to AngularJS
import { downgradeInjectable } from '@angular/upgrade/static';

angular.module('myApp')
  .factory('newService', downgradeInjectable(NewService));

// Use in AngularJS
angular.module('myApp').controller('OldController', function(newService) {
  console.log(newService.getData());
});
```

### Upgrading AngularJS → Angular
```typescript
// AngularJS service
angular.module('myApp').factory('oldService', function() {
  return {
    getData: function() {
      return 'data from AngularJS';
    }
  };
});

// Make available to Angular
import { InjectionToken } from '@angular/core';

export const OLD_SERVICE = new InjectionToken<any>('oldService');

@NgModule({
  providers: [
    {
      provide: OLD_SERVICE,
      useFactory: (i: any) => i.get('oldService'),
      deps: ['$injector']
    }
  ]
})

// Use in Angular
@Component({...})
export class NewComponent {
  constructor(@Inject(OLD_SERVICE) private oldService: any) {
    console.log(this.oldService.getData());
  }
}
```

## Routing Migration

```javascript
// Before: AngularJS routing
angular.module('myApp').config(function($routeProvider) {
  $routeProvider
    .when('/users', {
      template: '<user-list></user-list>'
    })
    .when('/users/:id', {
      template: '<user-detail></user-detail>'
    });
});
```

```typescript
// After: Angular routing
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

const routes: Routes = [
  { path: 'users', component: UserListComponent },
  { path: 'users/:id', component: UserDetailComponent }
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule {}
```

## Forms Migration

```html
<!-- Before: AngularJS -->
<form name="userForm" ng-submit="saveUser()">
  <input type="text" ng-model="user.name" required>
  <input type="email" ng-model="user.email" required>
  <button ng-disabled="userForm.$invalid">Save</button>
</form>
```

```typescript
// After: Angular (Template-driven)
@Component({
  template: `
    <form #userForm="ngForm" (ngSubmit)="saveUser()">
      <input type="text" [(ngModel)]="user.name" name="name" required>
      <input type="email" [(ngModel)]="user.email" name="email" required>
      <button [disabled]="userForm.invalid">Save</button>
    </form>
  `
})

// Or Reactive Forms (preferred)
import { FormBuilder, FormGroup, Validators } from '@angular/forms';

@Component({
  template: `
    <form [formGroup]="userForm" (ngSubmit)="saveUser()">
      <input formControlName="name">
      <input formControlName="email">
      <button [disabled]="userForm.invalid">Save</button>
    </form>
  `
})
export class UserFormComponent {
  userForm: FormGroup;

  constructor(private fb: FormBuilder) {
    this.userForm = this.fb.group({
      name: ['', Validators.required],
      email: ['', [Validators.required, Validators.email]]
    });
  }

  saveUser() {
    console.log(this.userForm.value);
  }
}
```

## Migration Timeline

```
Phase 1: Setup (1-2 weeks)
- Install Angular CLI
- Set up hybrid app
- Configure build tools
- Set up testing

Phase 2: Infrastructure (2-4 weeks)
- Migrate services
- Migrate utilities
- Set up routing
- Migrate shared components

Phase 3: Feature Migration (varies)
- Migrate feature by feature
- Test thoroughly
- Deploy incrementally

Phase 4: Cleanup (1-2 weeks)
- Remove AngularJS code
- Remove ngUpgrade
- Optimize bundle
- Final testing
```

## Resources

- **references/hybrid-mode.md**: Hybrid app patterns
- **references/component-migration.md**: Component conversion guide
- **references/dependency-injection.md**: DI migration strategies
- **references/routing.md**: Routing migration
- **assets/hybrid-bootstrap.ts**: Hybrid app template
- **assets/migration-timeline.md**: Project planning
- **scripts/analyze-angular-app.sh**: App analysis script

## Best Practices

1. **Start with Services**: Migrate services first (easier)
2. **Incremental Approach**: Feature-by-feature migration
3. **Test Continuously**: Test at every step
4. **Use TypeScript**: Migrate to TypeScript early
5. **Follow Style Guide**: Angular style guide from day 1
6. **Optimize Later**: Get it working, then optimize
7. **Document**: Keep migration notes

## Common Pitfalls

- Not setting up hybrid app correctly
- Migrating UI before logic
- Ignoring change detection differences
- Not handling scope properly
- Mixing patterns (AngularJS + Angular)
- Inadequate testing

## Limitations
- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.