In the world of web application development, Angular is considered one of the best open-source JavaScript frameworks.

Google's Angular team announced that Angular 4 would be released on 23 March. Actually, they skipped version 3. As all of you know, the long awaited release of Angular 2 was a complete makeover of its previous version.

It is just awesome for old developers. However, for new developers who are still in the learning phase, it could be a little confusing and tricky. Anyway, this article will offer a comparison of Angular 2 and Angular 4.

Angular 2

Angular 2 was released at the end of 2015. Let's take a look at why this version was released and what it added to web development. 

This version of Angular was more focused on the development of mobile apps, as it allowed developers to create cross platform applications. The reason is that it is easier to handle the desktop component of things after the challenges connected to mobile apps (functionality, load time, etc.) have been addressed.

Numerous modules were eliminated out of Angular's core, which led to better performance. These made their way to Angular's ever-growing ecosystem of modules, which means that you have the ability to select and choose the components you want.

Angular 2.0 was aimed at ES6 and "evergreen" modern browsers (these automatically update to the most recent version). Building for these browsers means various hacks and workarounds that make Angular harder to develop can be eliminated, allowing developers to concentrate on the code linked to their company domain.

Angular 2 Features and Performance

AtScript is a superset of ES6 and it was used to help develop Angular 2. It is processed from the Traceur compiler (combined with ES6) to generate ES5 code and utilizes TypeScript's syntax to create runtime type assertions rather than compile time tests. But, AtScript is not mandatory--you still have the ability to use plain JavaScript/ES5 code rather than AtScript to compose Angular apps.

Improved Dependency Injection (DI):

Dependency injection (a program design pattern where an item is passed its own dependencies, as opposed to producing them) was among the aspects that originally differentiated Angular from its competitors. Dependency Injection is very helpful when it comes to modular development and element isolation, yet its implementation has been plagued with issues since Angular 1.x. Angular 2 handled these problems, in addition to adding missing features like kid injectors along with lifetime/scope control.

Annotation:

AtScript supplies tools for linking metadata with functions. This eases the building of object instances by supplying the essential information into the DI library (that will check for related meta data if calling a function or creating the instance of a class). It'll also be simple to override parameter information by providing an Inject annotation.

Child Injectors:

A kid injector inherits all of the professional services of its parent together with the capacity to override them at the child level. According to demand, several kinds of objects could be called out and mechanically overridden in a variety of scopes.

Instance Scope:

The enhanced DI library is comprised of instance scope controllers, which are even stronger when used with child injectors along with your scope identifiers.

Dynamic Loading:

This is a feature which was not available in the previous version(s) of Angular. It was addressed by Angular 2, however, which allowed programmers to add new directives or controls on the fly.

Templating:

In Angular 2, the template compilation procedure is asynchronous. Since the code relies on the ES6 module, the module loader will load dependencies simply by referencing them at the part component.

Directives:

Three kinds of Directives were made available for Angular 2: 

• Component Directives: They made components reusable by encapsulating logic in HTML, CSS, and JavaScript.
• Decorator Directives: They can be used to decorate elements (for example, Hiding/Showing elements by ng-hide/ng-show or adding a tooltip).
• Template Directives: These can turn HTML into a reusable template. The instantiating of this template and its insertion into the DOM could be completely controlled by the directive writer. Examples include ng-repeat and ng-if.

Child Router:

The Child router will convert every part of the program to a more compact application by supplying it with its own router. It helps to encapsulate the entire feature collections of a program.

Screen Activator:

With Angular 2, developers were able to take finer control on the navigation life cycle, through a set of can* callbacks.

• canActivate: It will allow or prevent navigation to the new control.
• activate: It will respond to successful navigation to the new control.
• canDeactivate: It will prevent or allow navigation away from the old controller.
• deactivate: It will respond to successful navigation away from the old controller.

Design:

All this logic was built using a pipeline architecture that made it incredibly simple to add one's own actions into the pipeline or remove default ones. Moreover, its asynchronous character allowed developers to some make server requests to authenticate a user or load information for a control, while still in the pipeline.

Logging:

Angular 2.0 included a logging service known as diary.js--a very helpful attribute which measures where time is invested in your program (thus permitting you to identify bottlenecks in your code).

Scope:

$scope was removed from Angular 2.

Angular 4 Features and Performance

As compared to Angular 2, there are lots of new items added to this list. Not just new features but also some tweaks that improved old capabilities. So let's move on to see the list.

Smaller and Faster:

With Angular 4, programs will consume less space and run quicker than previous versions. And the staff is focused on continually making additional improvements.

View Engine:

They have made adjustments under to hood to exactly what AOT created code looks like. These modifications decrease the size of the generated code for those parts by approximately 60 percent. The more complicated the templates are, the greater the savings.

Animation Package:

They've pulled animations from the Angular core and set them in their own package. This means that in case you don't use animations, this excess code won't end up on your creation packages.
This feature will also enable you to easily find docs and to take advantage of auto-completion. You may add animations to the main NgModule by importing the Browser Animations Module out of @angular/platform-browser/animations.

Improved *ngIf and *ngFor:

The template binding syntax currently supports a few helpful alterations. Now you can utilize an if/else design syntax, and assign local variables like if to unroll an observable.

Angular Universal:

This release now contains the results of the external and internal work from the Universal team throughout the last few months. The vast majority of this Universal code is currently located in @angular/platform-server.

To learn more about using Angular Universal, have a look at the new renderModuleFactory method in @angular/platform-server, or Rob Wormald's Demo Repository. More documentation and code samples will come.

TypeScript 2.1 and 2.2 Compatibility:

The group has upgraded Angular into a more recent version of TypeScript. This will enhance the rate of ngc and you'll receive far better type checking during your program.

Source Maps for Templates:

Now whenever there's an error caused by something in one of the templates, they create source maps that provide a meaningful context concerning the original template.

Conclusion:

As I said earlier, Angular will be a bit confusing for those who are still in the learning phase. But for experienced developers who have knowledge of version 2, then it will be very easy for them to use and they will find it very helpful.