Source: wshobson/agents Original Plugin: framework-migration

Angular Migration

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

When to Use This Skill

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

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

Start with Services: Migrate services first (easier)
Incremental Approach: Feature-by-feature migration
Test Continuously: Test at every step
Use TypeScript: Migrate to TypeScript early
Follow Style Guide: Angular style guide from day 1
Optimize Later: Get it working, then optimize
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