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What's New in Angular 4? [Angular 4 New Features]

Angular 4 contains some additional Enhancement and Improvement. Consider the following enhancements.
1.      Smaller & Faster Apps
2.      View Engine Size Reduce
3.      Animation Package
4.      NgIf and ngFor Improvement
5.      Template
6.      NgIf with Else
7.      Use of AS keyword
8.      Pipes
9.      HTTP Request Simplified
10.   Apps Testing Simplified
11.   Introduce Meta Tags
12.   Added some Forms Validators Attributes
13.   Added Compare Select Options
14.   Enhancement in Router
15.   Added Optional Parameter
16.   Improvement Internationalization

1. Smaller & Faster Apps - Angular 4 applications is smaller & faster in comparison with Angular 2.

2. View Engine Size Reduce - Some changes under to hood to what AOT generated code compilation that means in Angular 4, improved the compilation time. These changes reduce around 60% size in most cases.

3. Animation Package- Animations now have their own package i.e. @angular/platform-browser/animations

4. Improvement - Some Improvement on *ngIf and *ngFor.




5. Template - The template is now ng-template. You should use the “ng-template” tag instead of “template”. Now Angular has its own template tag that is called “ng-template”.

6. NgIf with Else – Now in Angular 4, possible to use an else syntax as,

<div *ngIf="user.length > 0; else empty"><h2>Users</h2></div>
<ng-template #empty><h2>No users.</h2></ng-template>

7. AS keyword – A new addition to the template syntax is the “as keyword” is use to simplify to the “let” syntax.

Use of as keyword,
<div *ngFor="let user of users | slice:0:2 as total; index as = i">
    {{i+1}}/{{total.length}}: {{user.name}}
</div>

To subscribe only once to a pipe “|” with “async” and If a user is an observable, you can now use to write,

<div *ngIf="users | async as usersModel">
    <h2>{{ usersModel.name }}</h2> <small>{{ usersModel.age }}</small>
</div>


8. Pipes - Angular 4 introduced a new “titlecase” pipe “|” and use to changes the first letter of each word into the uppercase. 

The example as,
<h2>{{ 'anil singh' | titlecase }}</h2>
<!-- OUPPUT - It will display 'Anil Singh' -->

9. Http - Adding search parameters to an “HTTP request” has been simplified as,

//Angular 4 -
http.get(`${baseUrl}/api/users`, { params: { sort: 'ascending' } });

//Angular 2-
const params = new URLSearchParams();
params.append('sort', 'ascending');
http.get(`${baseUrl}/api/users`, { search: params });

10. Test- Angular 4, overriding a template in a test has also been simplified as,

//Angular 4 -
TestBed.overrideTemplate(UsersComponent, '<h2>{{users.name}}</h2>');

//Angular 2 -
TestBed.overrideComponent(UsersComponent, {
    set: { template: '<h2>{{users.name}}</h2>' }
});

11. Service- A new service has been introduced to easily get or update “Meta Tags” i.e.
@Component({
    selector: 'users-app',
    template: `<h1>Users</h1>`
})
export class UsersAppComponent {
    constructor(meta: Meta) {
        meta.addTag({ name: 'Blogger', content: 'Anil Singh' });
    }
}

12. Forms Validators - One new validator joins the existing “required”, “minLength”, “maxLength” and “pattern”. An email helps you validate that the input is a valid email.

13. Compare Select Options - A new “compareWith” directive has been added and it used to help you compare options from a select.

<select [compareWith]="byUId" [(ngModel)]="selectedUsers">
    <option *ngFor="let user of users" [ngValue]="user.UId">{{user.name}}</option>
</select>

14. Router - A new interface “paramMap” and “queryParamMap” has been added and it introduced to represent the parameters of a URL. 

const uid = this.route.snapshot.paramMap.get('UId');
this.userService.get(uid).subscribe(user => this.name = name);

15. CanDeactivate - This “CanDeactivate” interface now has an extra (optional) parameter and it is containing the next state.

16. I18n - The internationalization is tiny improvement.

//Angular 4-
<div [ngPlural]="value">
    <ng-template ngPluralCase="0">there is nothing</ng-template>
    <ng-template ngPluralCase="1">there is one</ng-template>
</div>

//Angular 2-
<div [ngPlural]="value">
    <ng-template ngPluralCase="=0">there is nothing</ng-template>
    <ng-template ngPluralCase="=1">there is one</ng-template>
</div>

Stayed Informed – Angular 2 vs. React.Js
Stayed Informed – Best Angular 2 Interview Q/A

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