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