Step by Step for Creating Your First Angular Element

Dhananjay Kumar / Friday, July 06, 2018

Angular Elements allow us to create reusable Angular components, which can be used outside of the Angular application. You can use an Angular Element in any other application such as normal HTML, React, etc.  Essentially, Angular Elements are normal components, which are packaged as Custom Elements. You can learn more about Custom Elements here.

Angular Elements are reusable components, which can be used outside Angular.  You can learn more about

We will keep things simple in this post and, in a step by step manner, learn to create a basic Angular Element. So, let us get started.

Step 1: Installation

Create a new project using Angular CLI 

ng new demo1

Once the project is created, change directory to demo1 and install Angular Elements. For that, run an npm command, as shown below:

npm install @angular/elements

To work with older browsers, we need polyfill. So, let us install that also as shown below:

npm install @webcomponents/custom-elements

 After installing polyfill, open polyfills.ts file and add these two entries:

import '@webcomponents/custom-elements/src/native-shim';
import '@webcomponents/custom-elements/custom-elements.min';

Step 2: Create the Component

In this step, we will create a reusable component, which would be used as an Angular Element.

   import { Component, Input } from '@angular/core';
 
  @Component({
      selector: 'app-message',
      template: `
 <h1 style='text-center'>{{title}}</h1>
  <h2>hey {{name}} loving Angular Elements {{answer}}</h2>
`,
      styles: ['h2 {color:red;}']
  })
  export class MessageComponent {
      title = 'Angular Elements';
      @Input() name: string;
      @Input() answer: string;
  }

MessageComponent is a very simple component with two properties decorated with the @Input() decorator.

Step 3: Register the Component

 To register a component to be used as an Angular Element, we need to perform following tasks:

  • Import component.
  • Pass it in declarations array.
  • Pass component in entryComponents array.
  • Do not pass any component in bootstrap array.
import { BrowserModule } from '@angular/platform-browser';
 import { NgModule } from '@angular/core';
 import { MessageComponent } from './message.component';
 
 @NgModule({
     declarations: [
         MessageComponent
     ],
     imports: [
         BrowserModule
     ],
     providers: [],
     bootstrap: [],
     entryComponents: [MessageComponent]
 })
 export class AppModule {
 
 }

We do not need to bootstrap custom elements. They will be created automatically when added to the DOM and destroyed when removed from the DOM, however, they have to created somehow hence we are adding them in entryComponents array. You must be knowing this property from dynamic component.

Step 4: Create Element from the component

 We need to invoke createCustomElement to create a custom element from an Angular Component. To do that, first import following items in angular.module.ts

import { NgModule, Injector } from '@angular/core';
import { createCustomElement } from '@angular/elements';

After importing required modules in the AppModule, we need to create custom element as shown in the listing below. Also, we are manually calling ngDoBootstrap.

export class AppModule {
 
      constructor(private injector: Injector) {
          const customElement = createCustomElement(MessageComponent, { injector });
          customElements.define('app-message', customElement);
      }
 
      ngDoBootstrap() {
 
      }
  }

Step 5: Use Custom Element

Ideally, we will use the custom element in any external html file. In a further article, we will cover that. To use created custom element in index.html of same angular application, just place it in body, as shown below:

<body>
        <!-- <app-root></app-root> -->
        <app-message name="dj" answer="yes"></app-message>
</body>

Now run the application using command ng serve and you should have custom element rendered, as shown in below image:

Therefore, we can conclude that to work with Angular Custom Element, we need to perform following steps:

  1. Install @angular/elements
  2. Create component
  3. Register component in entryComponent
  4. Invoke createElement to create custom element
  5. Use it on html

 I hope you find this post useful. Thanks for reading.  If you like this post, please share it. Also, if you have not checked out Infragistics Ignite UI for Angular Components, be sure to do so! They have 30+ material based Angular components to help you code web apps faster.