Know the Difference Between Angular 2 and Angular 4 latest version.

Key Difference: Angular 4 adds a number of newer features to Angular 2, while still being backward compatible. It also allows the programs developed on Angular 4 to consume less space and run faster, which in turn reduces the size of the application and increasing its speed.

Angular is a software that has been created by Google. The primary purpose of Angular is to create web-based software. Applications created on Angular are intended to live on the web, mobile, or the desktop. The official description of Angular describes it as an “open-source front-end web application platform” that is based on TypeScript, which in turn is an open-source programming language developed and maintained by Microsoft and influenced by JavaScript.

Before Angular 2 or Angular 4 came the AngularJS. However, it should be noted Angular is not the same program as AngularJS. In fact, it can be said that Angular is a complete rewrite of AngularJS. Due to the limitations of AngularJS, a new rewrite of Angular was commissioned. This version was called Angular 2 by the original team, however, this led to confusion, as this version was completely different from AngularJS. Hence, it was decided instead of calling it a second version of AngularJS, it will be called just Angular, a completely different program. The first version of Angular was called Angular 2, the name stuck around, as it was the second version of the original program, while the AngularJS versions were called Version 1.X.

Angular 2 was announced at the ng-Europe conference on September 22-23, 2014, while the final version was released on September 14, 2016. Angular 4, on the other hand, was announced on December 13, 2016, and the final version launched on March 23, 2017. Angular 3 was skipped in order to avoid confusion, as the router package's version of Angular was already being distributed as v3.3.0 due to a misalignment of version numbers.

One of the main benefits of Angular 4 is that it cuts down on bundled file size by 60% as compared to Angular 2. It is also backward compatible with Angular 2, as well as compatible with the newer versions of TypeScript, such as TypeScript 2.1 and TypeScript 2.2. The benefit of which is that it improves type checking and also enhances IDE features for Visual Studio Code.

Additionally, in Angular 4, the code generated is reduced when compared to Angular 2. Application development has also been accelerated in Angular 4. The code generated in Angular 4 can also be used in debug mode and production mode. Furthermore, instance developers can add new directives and controls. Angular 4 also has various component splitting features which have increased code reusability.

Angular 4 introduced a view engine, which decreases the size of the generated code. It does so using the Ahead of Time (AOT) manner. Also, in Angular 2 the Angular animation function requires the @angular/code module, which essentially creates its own package. In Angular 4, the animation package in no longer used, which helps reduce the size of the code.

Angular 4 also features an improved *ngIf and *ngFor. It can now utilize an if/else design syntax. It can also assign local variables like if to unroll an observable. Angular 4 also contains the external and internal work from Universal, which is located in @angular/platform-server. Angular 4 further introduces source maps which can help provide a meaningful context concerning the original template, as it allows one to map errors caused by something in one of the templates.

In short, Angular 4 adds a number of newer features to Angular 2, while still being backward compatible. It also allows the programs developed on Angular 4 to consume less space and run faster, which in turn reduces the size of the application and increasing its speed.

Comparison between Angular 2 and Angular 4:

	Angular 2	Angular 4
Program	Angular	Angular
Launched	September 14, 2016	March 23, 2017
Backward Compatibility	Not compatible with AngularJS.	Angular 4 is backward compatible with Angular 2
Compatibility with TypeScript	Compatible with TypeScript 2.0. Not compatible with TypeScript 2.1 and TypeScript 2.2.	Compatible with TypeScript 2.1 and TypeScript 2.2
File Size	60% larger bundled file size as compared to Angular 2	60% Reduced bundled file size as compared to Angular 4
Directives and controls	Limited directives and controls	New directives and controls
Component splitting features	Limited to no component splitting features	Component splitting features
Code reusability	Limited code reusability	Increased code reusability
Application development	Slower application development as compared to Angular 4	Accelerated application development as compared to Angular 2
Ahead of Time (AOT)	No Ahead of Time (AOT)	Introduced Ahead of Time (AOT)
View Engine	No view engine	Introduced view engine
Animation Function	The Angular animation function requires the @angular/code module, essentially creating its own package.	Animation package is not required, which reduces the size of the code.
*ngIf and *ngFor	Limited *ngIf and *ngFor. Can’t utilize an if/else design syntax, and assign local variables	Improved *ngIf and *ngFor. Can utilize an if/else design syntax, and assign local variables like if to unroll an observable
Angular Universal	Does not contain the external and internal work from Universal	Contains the external and internal work from Universal
Source maps	Does not contain source maps	Source maps that provide a meaningful context concerning the original template