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AngularJS to Angular Concepts: Quick Reference

Angular is the name for the Angular of today and tomorrow. AngularJS is the name for all v1.x versions of Angular.

This guide helps you transition from AngularJS to Angular by mapping AngularJS syntax to the equivalent Angular syntax.

See the Angular syntax in this .

Template basics

Templates are the user-facing part of an Angular application and are written in HTML. The following table lists some of the key AngularJS template features with their equivalent Angular template syntax.

AngularJS Angular

Bindings/interpolation

Your favorite hero is: {{vm.favoriteHero}}

In AngularJS, an expression in curly braces denotes one-way binding. This binds the value of the element to a property in the controller associated with this template.

When using the controller as syntax, the binding is prefixed with the controller alias (vm or $ctrl) because you have to be specific about the source of the binding.

Bindings/interpolation

Your favorite hero is: {{favoriteHero}}

In Angular, a template expression in curly braces still denotes one-way binding. This binds the value of the element to a property of the component. The context of the binding is implied and is always the associated component, so it needs no reference variable.

For more information, see the Interpolation section of the Template Syntax page.

Filters

<td>{{movie.title | uppercase}}</td>

To filter output in AngularJS templates, use the pipe character (|) and one or more filters.

This example filters the title property to uppercase.

Pipes

<td>{{movie.title | uppercase}}</td>

In Angular you use similar syntax with the pipe (|) character to filter output, but now you call them pipes. Many (but not all) of the built-in filters from AngularJS are built-in pipes in Angular.

For more information, see Filters/pipes below.

Local variables

<tr ng-repeat="movie in vm.movies">
          <td>{{movie.title}}</td>
        </tr>

Here, movie is a user-defined local variable.

Input variables

<tr *ngFor="let movie of movies">
  <td>{{movie.title}}</td>
</tr>

Angular has true template input variables that are explicitly defined using the let keyword.

For more information, see the ngFor micro-syntax section of the Template Syntax page.

Template directives

AngularJS provides more than seventy built-in directives for templates. Many of them aren't needed in Angular because of its more capable and expressive binding system. The following are some of the key AngularJS built-in directives and their equivalents in Angular.

AngularJS Angular

ng-app

<body ng-app="movieHunter">

The application startup process is called bootstrapping.

Although you can bootstrap an AngularJS app in code, many applications bootstrap declaratively with the ng-app directive, giving it the name of the application's module (movieHunter).

Bootstrapping

import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';
import { environment } from './environments/environment';

if (environment.production) {
  enableProdMode();
}

platformBrowserDynamic().bootstrapModule(AppModule);
import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent }  from './app.component';

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ AppComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule { }

Angular doesn't have a bootstrap directive. To launch the app in code, explicitly bootstrap the application's root module (AppModule) in main.ts and the application's root component (AppComponent) in app.module.ts.

ng-class

<div ng-class="{active: isActive}">
        <div ng-class="{active: isActive,
                           shazam: isImportant}">

In AngularJS, the ng-class directive includes/excludes CSS classes based on an expression. That expression is often a key-value control object with each key of the object defined as a CSS class name, and each value defined as a template expression that evaluates to a Boolean value.

In the first example, the active class is applied to the element if isActive is true.

You can specify multiple classes, as shown in the second example.

ngClass

<div [ngClass]="{'active': isActive}">
<div [ngClass]="{'active': isActive,
                 'shazam': isImportant}">
<div [class.active]="isActive">

In Angular, the ngClass directive works similarly. It includes/excludes CSS classes based on an expression.

In the first example, the active class is applied to the element if isActive is true.

You can specify multiple classes, as shown in the second example.

Angular also has class binding, which is a good way to add or remove a single class, as shown in the third example.

For more information see the Attribute, class, and style bindings section of the Template Syntax page.

ng-click

<button ng-click="vm.toggleImage()">
        <button ng-click="vm.toggleImage($event)">

In AngularJS, the ng-click directive allows you to specify custom behavior when an element is clicked.

In the first example, when the user clicks the button, the toggleImage() method in the controller referenced by the vm controller as alias is executed.

The second example demonstrates passing in the $event object, which provides details about the event to the controller.

Bind to the click event

<button (click)="toggleImage()">
<button (click)="toggleImage($event)">

AngularJS event-based directives do not exist in Angular. Rather, define one-way binding from the template view to the component using event binding.

For event binding, define the name of the target event within parenthesis and specify a template statement, in quotes, to the right of the equals. Angular then sets up an event handler for the target event. When the event is raised, the handler executes the template statement.

In the first example, when a user clicks the button, the toggleImage() method in the associated component is executed.

The second example demonstrates passing in the $event object, which provides details about the event to the component.

For a list of DOM events, see: https://developer.mozilla.org/en-US/docs/Web/Events.

For more information, see the Event binding section of the Template Syntax page.

ng-controller

<div ng-controller="MovieListCtrl as vm">

In AngularJS, the ng-controller directive attaches a controller to the view. Using the ng-controller (or defining the controller as part of the routing) ties the view to the controller code associated with that view.

Component decorator

@Component({
  selector: 'app-movie-list',
  templateUrl: './movie-list.component.html',
  styleUrls: [ './movie-list.component.css' ],
})

In Angular, the template no longer specifies its associated controller. Rather, the component specifies its associated template as part of the component class decorator.

For more information, see Architecture Overview.

ng-hide

In AngularJS, the ng-hide directive shows or hides the associated HTML element based on an expression. For more information, see ng-show.

Bind to the hidden property

In Angular, you use property binding; there is no built-in hide directive. For more information, see ng-show.

ng-href

<a ng-href="{{ angularDocsUrl }}">Angular Docs</a>

The ng-href directive allows AngularJS to preprocess the href property so that it can replace the binding expression with the appropriate URL before the browser fetches from that URL.

In AngularJS, the ng-href is often used to activate a route as part of navigation.

<a ng-href="#{{ moviesHash }}">Movies</a>

Routing is handled differently in Angular.

Bind to the href property

<a [href]="angularDocsUrl">Angular Docs</a>

Angular uses property binding; there is no built-in href directive. Place the element's href property in square brackets and set it to a quoted template expression.

For more information see the Property binding section of the Template Syntax page.

In Angular, href is no longer used for routing. Routing uses routerLink, as shown in the following example.

<a [routerLink]="['/movies']">Movies</a>

For more information on routing, see the RouterLink binding section of the Routing & Navigation page.

ng-if

<table ng-if="movies.length">

In AngularJS, the ng-if directive removes or recreates a portion of the DOM, based on an expression. If the expression is false, the element is removed from the DOM.

In this example, the <table> element is removed from the DOM unless the movies array has a length greater than zero.

*ngIf

<table *ngIf="movies.length">

The *ngIf directive in Angular works the same as the ng-if directive in AngularJS. It removes or recreates a portion of the DOM based on an expression.

In this example, the <table> element is removed from the DOM unless the movies array has a length.

The (*) before ngIf is required in this example. For more information, see Structural Directives.

ng-model

<input ng-model="vm.favoriteHero"/>

In AngularJS, the ng-model directive binds a form control to a property in the controller associated with the template. This provides two-way binding, whereby any change made to the value in the view is synchronized with the model, and any change to the model is synchronized with the value in the view.

ngModel

<input [(ngModel)]="favoriteHero" />

In Angular, two-way binding is denoted by [()], descriptively referred to as a "banana in a box". This syntax is a shortcut for defining both property binding (from the component to the view) and event binding (from the view to the component), thereby providing two-way binding.

For more information on two-way binding with ngModel, see the NgModel—Two-way binding to form elements with [(ngModel)] section of the Template Syntax page.

ng-repeat

<tr ng-repeat="movie in vm.movies">

In AngularJS, the ng-repeat directive repeats the associated DOM element for each item in the specified collection.

In this example, the table row (<tr>) element repeats for each movie object in the collection of movies.

*ngFor

<tr *ngFor="let movie of movies">

The *ngFor directive in Angular is similar to the ng-repeat directive in AngularJS. It repeats the associated DOM element for each item in the specified collection. More accurately, it turns the defined element (<tr> in this example) and its contents into a template and uses that template to instantiate a view for each item in the list.

Notice the other syntax differences: The (*) before ngFor is required; the let keyword identifies movie as an input variable; the list preposition is of, not in.

For more information, see Structural Directives.

ng-show

<h3 ng-show="vm.favoriteHero">
          Your favorite hero is: {{vm.favoriteHero}}
        </h3>

In AngularJS, the ng-show directive shows or hides the associated DOM element, based on an expression.

In this example, the <div> element is shown if the favoriteHero variable is truthy.

Bind to the hidden property

<h3 [hidden]="!favoriteHero">
  Your favorite hero is: {{favoriteHero}}
</h3>

Angular uses property binding; there is no built-in show directive. For hiding and showing elements, bind to the HTML hidden property.

To conditionally display an element, place the element's hidden property in square brackets and set it to a quoted template expression that evaluates to the opposite of show.

In this example, the <div> element is hidden if the favoriteHero variable is not truthy.

For more information on property binding, see the Property binding section of the Template Syntax page.

ng-src

<img ng-src="{{movie.imageurl}}">

The ng-src directive allows AngularJS to preprocess the src property so that it can replace the binding expression with the appropriate URL before the browser fetches from that URL.

Bind to the src property

<img [src]="movie.imageurl">

Angular uses property binding; there is no built-in src directive. Place the src property in square brackets and set it to a quoted template expression.

For more information on property binding, see the Property binding section of the Template Syntax page.

ng-style

<div ng-style="{color: colorPreference}">

In AngularJS, the ng-style directive sets a CSS style on an HTML element based on an expression. That expression is often a key-value control object with each key of the object defined as a CSS property, and each value defined as an expression that evaluates to a value appropriate for the style.

In the example, the color style is set to the current value of the colorPreference variable.

ngStyle

<div [ngStyle]="{'color': colorPreference}">
<div [style.color]="colorPreference">

In Angular, the ngStyle directive works similarly. It sets a CSS style on an HTML element based on an expression.

In the first example, the color style is set to the current value of the colorPreference variable.

Angular also has style binding, which is good way to set a single style. This is shown in the second example.

For more information on style binding, see the Style binding section of the Template Syntax page.

For more information on the ngStyle directive, see NgStyle section of the Template Syntax page.

ng-switch

<div ng-switch="vm.favoriteHero &&
                        vm.checkMovieHero(vm.favoriteHero)">
            <div ng-switch-when="true">
              Excellent choice!
            </div>
            <div ng-switch-when="false">
              No movie, sorry!
            </div>
            <div ng-switch-default>
              Please enter your favorite hero.
            </div>
        </div>

In AngularJS, the ng-switch directive swaps the contents of an element by selecting one of the templates based on the current value of an expression.

In this example, if favoriteHero is not set, the template displays "Please enter ...". If favoriteHero is set, it checks the movie hero by calling a controller method. If that method returns true, the template displays "Excellent choice!". If that methods returns false, the template displays "No movie, sorry!".

ngSwitch

<span [ngSwitch]="favoriteHero &&
               checkMovieHero(favoriteHero)">
  <p *ngSwitchCase="true">
    Excellent choice!
  </p>
  <p *ngSwitchCase="false">
    No movie, sorry!
  </p>
  <p *ngSwitchDefault>
    Please enter your favorite hero.
  </p>
</span>

In Angular, the ngSwitch directive works similarly. It displays an element whose *ngSwitchCase matches the current ngSwitch expression value.

In this example, if favoriteHero is not set, the ngSwitch value is null and *ngSwitchDefault displays, "Please enter ...". If favoriteHero is set, the app checks the movie hero by calling a component method. If that method returns true, the app selects *ngSwitchCase="true" and displays: "Excellent choice!" If that methods returns false, the app selects *ngSwitchCase="false" and displays: "No movie, sorry!"

The (*) before ngSwitchCase and ngSwitchDefault is required in this example.

For more information, see The NgSwitch directives section of the Template Syntax page.

Filters/pipes

Angular pipes provide formatting and transformation for data in the template, similar to AngularJS filters. Many of the built-in filters in AngularJS have corresponding pipes in Angular. For more information on pipes, see Pipes.

AngularJS Angular

currency

<td>{{movie.price | currency}}</td>

Formats a number as currency.

currency

<td>{{movie.price | currency:'USD':true}}</td>

The Angular currency pipe is similar although some of the parameters have changed.

date

<td>{{movie.releaseDate | date}}</td>

Formats a date to a string based on the requested format.

date

<td>{{movie.releaseDate | date}}</td>

The Angular date pipe is similar.

filter

<tr ng-repeat="movie in movieList | filter: {title:listFilter}">

Selects a subset of items from the defined collection, based on the filter criteria.

none

For performance reasons, no comparable pipe exists in Angular. Do all your filtering in the component. If you need the same filtering code in several templates, consider building a custom pipe.

json

<pre>{{movie | json}}</pre>

Converts a JavaScript object into a JSON string. This is useful for debugging.

json

<pre>{{movie | json}}</pre>

The Angular json pipe does the same thing.

limitTo

<tr ng-repeat="movie in movieList | limitTo:2:0">

Selects up to the first parameter (2) number of items from the collection starting (optionally) at the beginning index (0).

slice

<tr *ngFor="let movie of movies | slice:0:2">

The SlicePipe does the same thing but the order of the parameters is reversed, in keeping with the JavaScript Slice method. The first parameter is the starting index; the second is the limit. As in AngularJS, coding this operation within the component instead could improve performance.

lowercase

<td>{{movie.title | lowercase}}</td>

Converts the string to lowercase.

lowercase

<td>{{movie.title | lowercase}}</td>

The Angular lowercase pipe does the same thing.

number

<td>{{movie.starRating | number}}</td>

Formats a number as text.

number

<td>{{movie.starRating | number}}</td>
<td>{{movie.starRating | number:'1.1-2'}}</td>
<td>{{movie.approvalRating | percent: '1.0-2'}}</td>

The Angular number pipe is similar. It provides more functionality when defining the decimal places, as shown in the second example above.

Angular also has a percent pipe, which formats a number as a local percentage as shown in the third example.

orderBy

<tr ng-repeat="movie in movieList | orderBy : 'title'">

Displays the collection in the order specified by the expression. In this example, the movie title orders the movieList.

none

For performance reasons, no comparable pipe exists in Angular. Instead, use component code to order or sort results. If you need the same ordering or sorting code in several templates, consider building a custom pipe.

Modules/controllers/components

In both AngularJS and Angular, modules help you organize your application into cohesive blocks of functionality.

In AngularJS, you write the code that provides the model and the methods for the view in a controller. In Angular, you build a component.

Because much AngularJS code is in JavaScript, JavaScript code is shown in the AngularJS column. The Angular code is shown using TypeScript.

AngularJS Angular

IIFE

(function () {
          ...
        }());

In AngularJS, an immediately invoked function expression (or IIFE) around controller code keeps it out of the global namespace.

none

This is a nonissue in Angular because ES 2015 modules handle the namespacing for you.

For more information on modules, see the Modules section of the Architecture Overview.

Angular modules

angular.module("movieHunter", ["ngRoute"]);

In AngularJS, an Angular module keeps track of controllers, services, and other code. The second argument defines the list of other modules that this module depends upon.

NgModules

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent }  from './app.component';

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ AppComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule { }

NgModules, defined with the NgModule decorator, serve the same purpose:

imports: specifies the list of other modules that this module depends upon declaration: keeps track of your components, pipes, and directives.

For more information on modules, see NgModules.

Controller registration

angular
          .module("movieHunter")
          .controller("MovieListCtrl",
                      ["movieService",
                       MovieListCtrl]);

AngularJS has code in each controller that looks up an appropriate Angular module and registers the controller with that module.

The first argument is the controller name. The second argument defines the string names of all dependencies injected into this controller, and a reference to the controller function.

Component decorator

@Component({
  selector: 'app-movie-list',
  templateUrl: './movie-list.component.html',
  styleUrls: [ './movie-list.component.css' ],
})

Angular adds a decorator to the component class to provide any required metadata. The @Component decorator declares that the class is a component and provides metadata about that component such as its selector (or tag) and its template.

This is how you associate a template with logic, which is defined in the component class.

For more information, see the Components section of the Architecture Overview page.

Controller function

function MovieListCtrl(movieService) {
        }

In AngularJS, you write the code for the model and methods in a controller function.

Component class

export class MovieListComponent {
}

In Angular, you create a component class to contain the data model and control methods. Use the TypeScript export keyword to export the class so that the functionality can be imported into NgModules.

For more information, see the Components section of the Architecture Overview page.

Dependency injection

MovieListCtrl.$inject = ['MovieService'];
        function MovieListCtrl(movieService) {
        }

In AngularJS, you pass in any dependencies as controller function arguments. This example injects a MovieService.

To guard against minification problems, tell Angular explicitly that it should inject an instance of the MovieService in the first parameter.

Dependency injection

constructor(movieService: MovieService) {
}

In Angular, you pass in dependencies as arguments to the component class constructor. This example injects a MovieService. The first parameter's TypeScript type tells Angular what to inject, even after minification.

For more information, see the Dependency injection section of the Architecture Overview.

Style sheets

Style sheets give your application a nice look. In AngularJS, you specify the style sheets for your entire application. As the application grows over time, the styles for the many parts of the application merge, which can cause unexpected results. In Angular, you can still define style sheets for your entire application. But now you can also encapsulate a style sheet within a specific component.

AngularJS Angular 
<link href="styles.css" rel="stylesheet" />

AngularJS, uses a link tag in the head section of the index.html file to define the styles for the application.

Styles configuration

"styles": [
  "styles.css"
],

With the Angular CLI, you can configure your global styles in the angular.json file. You can rename the extension to .scss to use sass.

StyleUrls

In Angular, you can use the styles or styleUrls property of the @Component metadata to define a style sheet for a particular component.

styleUrls: [ './movie-list.component.css' ],

This allows you to set appropriate styles for individual components that won’t leak into other parts of the application.

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https://v8.angular.io/guide/ajs-quick-reference