Angular vs AngularJS

When developers say "AngularJS" they mean version 1.x, released by Google in 2010. When they say "Angular" (without the JS), they mean versions 2 and above, which was a complete rewrite released in September 2016.

Despite sharing a name, these are two completely different frameworks. AngularJS reached End of Life (EOL) on December 31, 2021 — meaning no more official support, security patches, or bug fixes. If you are starting a new project today, use Angular (v2+).

Warning

Do not use AngularJS for new projects. It is no longer maintained. All code examples in this tutorial use modern Angular (v17+).

Why Was Angular Rewritten?

AngularJS had fundamental architectural limitations that made it difficult to:

Scale — large apps became slow because of digest cycle / dirty checking
Mobile-first — AngularJS was designed before mobile was a priority
Componentize — the shift to component-driven UI (influenced by React) required new primitives
Type-safe — JavaScript's loose typing caused runtime bugs at scale
Server-side render — AngularJS was purely client-side
Tree-shake — the entire framework was bundled even if you used only 10% of it

The team decided a clean rewrite in TypeScript, with a component model, reactive extensions (RxJS), and a proper Ahead-of-Time (AOT) compiler, was the right path forward.

Side-by-Side Comparison

Aspect	AngularJS (v1.x)	Angular (v2+)
Released	2010	2016
EOL	Dec 31, 2021	Actively maintained
Language	JavaScript	TypeScript
Architecture	MVC / MVW	Component-based
Data binding	$scope / $watch	@Input / @Output / Signals
Change detection	Digest cycle (dirty checking)	Zone.js + tree-based (Ivy)
Dependency injection	Simple injector	Hierarchical DI system
Routing	ngRoute / ui-router (3rd party)	@angular/router (built-in)
Forms	ngModel	Template-driven + Reactive forms
HTTP	$http service	HttpClient (Observable-based)
Rendering	DOM manipulation via $compile	Ivy renderer + AOT compilation
Mobile	Not optimized	Mobile-first design
Testing	Angular Mocks	TestBed + Jasmine/Jest
CLI	None official	Angular CLI (official)
Bundle size	Large (no tree-shaking)	Optimized (AOT + tree-shaking)
Learning curve	Moderate	Steeper initially

Architecture: MVC vs Component Tree

AngularJS followed an MVC (Model-View-Controller) pattern with $scope as the glue between models and views:

// AngularJS (1.x) — Controller with $scope
angular.module('myApp', [])
  .controller('GreetingController', function($scope) {
    $scope.greeting = 'Hello';
    $scope.name = 'World';
  });

HTML

<!-- AngularJS template -->
<div ng-app="myApp" ng-controller="GreetingController">
  <p>{{ greeting }}, {{ name }}!</p>
  <input ng-model="name" />
</div>

Modern Angular uses a component tree — every piece of UI is a self-contained component:

// Modern Angular (v17+) — Standalone component
import { Component } from '@angular/core';
import { FormsModule } from '@angular/forms';

@Component({
  selector: 'app-greeting',
  standalone: true,
  imports: [FormsModule],
  template: `
    <p>{{ greeting }}, {{ name }}!</p>
    <input [(ngModel)]="name" />
  `,
})
export class GreetingComponent {
  greeting = 'Hello';
  name = 'World';
}

Data Binding Differences

Both frameworks support two-way data binding, but the mechanism is very different.

Concept	AngularJS	Angular (v2+)
Two-way bind	ng-model (automatic)	[(ngModel)] or Signals (explicit)
One-way bind	{{ expression }}	{{ expression }} or [property]
Event handling	ng-click, ng-change, etc.	(click), (change), (input), etc.
Reference to element	$element (jQuery-like)	@ViewChild / ElementRef
Parent → child data	$scope inheritance (implicit)	@Input() (explicit)
Child → parent events	$emit / $broadcast	@Output() + EventEmitter

Change Detection: Digest Cycle vs Ivy

This is one of the most critical differences in terms of performance.

AngularJS Digest Cycle:

When any model changes, AngularJS runs a "digest cycle" — it checks every $watch registered in the app.
Each $watch compares the current value to the last known value.
If any value changed, it re-runs the cycle (up to 10 times).
In large applications with hundreds of watchers, this could cause noticeable lag.

Angular Ivy Change Detection:

Angular builds a component tree and only checks the subtree affected by a change.
With OnPush strategy, components only re-render when their inputs change.
With Signals (Angular 16+), change detection is surgical — only the signal's consumers update.

// Modern Angular — OnPush change detection strategy
import { Component, Input, ChangeDetectionStrategy } from '@angular/core';

@Component({
  selector: 'app-user-card',
  standalone: true,
  changeDetection: ChangeDetectionStrategy.OnPush,  // only re-render when @Input changes
  template: `<div>{{ user.name }}</div>`,
})
export class UserCardComponent {
  @Input() user!: { name: string };
}

Dependency Injection Differences

Both frameworks have DI, but Angular's is far more powerful.

// AngularJS — service with $inject annotation
angular.module('myApp')
  .service('UserService', ['$http', function($http) {
    this.getUser = function(id) {
      return $http.get('/api/users/' + id);
    };
  }]);

// Modern Angular — injectable service with TypeScript
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable({ providedIn: 'root' })  // available app-wide as a singleton
export class UserService {
  constructor(private http: HttpClient) {}

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

Tip

In Angular, providedIn: 'root' makes a service a singleton without registering it in any module — it is tree-shaken if unused.

Routing Comparison

// AngularJS routing with ngRoute
angular.module('myApp', ['ngRoute'])
  .config(function($routeProvider) {
    $routeProvider
      .when('/home', { templateUrl: 'home.html', controller: 'HomeController' })
      .when('/about', { templateUrl: 'about.html', controller: 'AboutController' })
      .otherwise({ redirectTo: '/home' });
  });

// Modern Angular — typed routes with lazy loading
import { Routes } from '@angular/router';

export const routes: Routes = [
  {
    path: 'home',
    loadComponent: () =>
      import('./home/home.component').then(m => m.HomeComponent),
  },
  {
    path: 'about',
    loadComponent: () =>
      import('./about/about.component').then(m => m.AboutComponent),
  },
  { path: '', redirectTo: 'home', pathMatch: 'full' },
];

Forms Comparison

Feature	AngularJS	Angular (v2+)
Binding approach	ng-model (always two-way)	Template-driven or Reactive (your choice)
Validation	ng-required, ng-pattern, etc.	Built-in validators + custom validator functions
Typed values	No — always strings	Yes — typed FormControl<T>
Programmatic control	Limited via $scope	Full via FormGroup / FormControl API
Dynamic forms	Difficult	Easy with FormArray

Should You Migrate from AngularJS?

Yes — if you have an AngularJS app, migration is strongly recommended because:

Security vulnerabilities — AngularJS no longer receives security patches.
Browser support — Modern browsers deprecate APIs that AngularJS depends on.
Performance — AngularJS apps are significantly slower than modern Angular.
Developer experience — No TypeScript, no modern tooling, harder to hire for.

Migration options:

ngUpgrade — run AngularJS and Angular side-by-side and migrate component by component.
Full rewrite — for smaller apps, a clean rewrite is often faster and cleaner.

AngularJS reached End of Life on December 31, 2021
Modern Angular (v2+) is a complete rewrite — not an upgrade
TypeScript, components, and Ivy replace $scope, controllers, and digest cycle
Angular CLI, lazy loading, and tree-shaking make modern Angular much faster
Use ngUpgrade if you must migrate incrementally