In web development, creating reusable UI components is important for building scalable applications. Angular, a powerful front-end framework, offers to create custom elements. In this article, we’ll explore more about the custom components and their uses.

Prerequisite:

• NPM or Nodejs
• Angular CLI
• Angular
• Typescript

What are Custom Components?

Custom elements in Angular 17 are a feature that allows you to create your own HTML elements with specific functionality and styling. These custom elements are essentially Angular components encapsulated within HTML tags, making them reusable and modular. The benefits of custom elements include improved code organization, easier maintenance, and enhanced reusability across different parts of an application or even in multiple projects.

Features of Custom Elements in Angular

• Encapsulation: Custom elements encapsulate both the UI and behavior of a particular feature or component, ensuring a clear separation of concerns and preventing unintended side effects.
• Reusability: Custom elements are designed to be reusable across different parts of an application. Once defined, they can be easily instantiated and used multiple times without duplicating code.
• Modularity: By breaking down UI components into custom elements, developers can create a modular architecture that promotes scalability and maintainability. Each custom element represents a self-contained module that can be developed, tested, and deployed independently.
• Flexibility: Custom elements in Angular offer flexibility in terms of customization and configuration. Developers can pass input properties, listen to output events, and apply styling to customize the behavior and appearance of custom elements as needed.
• Interoperability: Angular custom elements can be seamlessly integrated with other frameworks and libraries. They comply with web standards, making them compatible with various browsers and environments.

Uses of Custom Elements in Angular

• UI Components: Custom elements are commonly used to create UI components such as buttons, input fields, dropdown menus, modals, and cards. These components can be reused across different parts of an application to ensure consistency in design and user experience.
• Widgets and Plugins: Custom elements can be used to develop widgets, plugins, or standalone features that can be embedded into web pages or applications. Examples include interactive charts, maps, calendars, and social media integrations.
• Layout Components: Custom elements can represent layout components such as headers, footers, sidebars, and navigation menus. These components provide structural elements that define the layout and organization of a web page or application.
• Containers and Wrappers: Custom elements can act as containers or wrappers for other components or content. They provide a way to group related elements together and apply common styling or behavior to them.

Steps to Create Angular Application

Step 1: Install Angular CLI globally.

npm install -g @angular/cli

Step 2: Create Angular Application

ng new <-your-app-name->

Step 3: Navigate to app directory

cd <-your-app-name->

Project Structure:

Updated dependencies

"dependencies": {
    "@angular/animations": "^17.3.0",
    "@angular/common": "^17.3.0",
    "@angular/compiler": "^17.3.0",
    "@angular/core": "^17.3.0",
    "@angular/forms": "^17.3.0",
    "@angular/platform-browser": "^17.3.0",
    "@angular/platform-browser-dynamic": "^17.3.0",
    "@angular/platform-server": "^17.3.0",
    "@angular/router": "^17.3.0",
    "@angular/ssr": "^17.3.6",
    "express": "^4.18.2",
    "rxjs": "~7.8.0",
    "tslib": "^2.3.0",
    "zone.js": "~0.14.3"
  },

Step 4: Create a component (i.e. custom-element) to implement custom-element

ng generate component <-your-component-name-> //(custom-element)

Custom-element component

Example: This example demonstrates custom elements in Angular 17.

<!-- app.component.html -->

<app-custom-element text="This is my custom element!"></app-custom-element>
<h1>Angular 17 Custom Element Example</h1>

<!-- custom-element.component.html -->

<div>
    <h1>My Custom Element</h1>
    <p>{{ text }}</p>
</div>

// app.component.ts

import { Component, OnInit } from '@angular/core';
import { CustomElementComponent } from './custom-element/custom-element.component';

@Component({
    selector: 'app-root',
    standalone: true,
    imports: [CustomElementComponent],
    templateUrl: './app.component.html',
    styleUrl: './app.component.css'
})
export class AppComponent implements OnInit {
    constructor() { }
    ngOnInit(): void {
        throw new Error('Method not implemented.');
    }
}

// custom-element.component.ts

import { Component, OnInit, Input } from '@angular/core';

@Component({
    selector: 'app-custom-element',
    standalone: true,
    imports: [],
    templateUrl: './custom-element.component.html',
    styleUrl: './custom-element.component.css'
})
export class CustomElementComponent implements OnInit {
    @Input() text: string | undefined;

    constructor() { }

    ngOnInit() { }
}

Step 5: Serve your application.

ng serve

Output:

Output custom-element

FAQs

How are custom elements different from built-in HTML elements?

Built-in HTML elements are predefined elements provided by the browser, such as <div>, <span>, and <input>, while custom elements are created by developers to meet specific application requirements. Custom elements offer greater flexibility and reusability compared to built-in elements.

How do I create a custom element in Angular?

To create a custom element in Angular, you define a new component using Angular CLI or manually, then register the component as a custom element using Angular’s createCustomElement function provided by the @angular/elements package.

Can I pass data to custom elements in Angular?

Yes, you can pass data to custom elements in Angular using input properties. Input properties allow you to bind data from the parent component to the custom element, enabling dynamic behavior and customization.

How do I handle events in custom elements in Angular?

You can handle events in custom elements using event binding and event emitters. Event binding allows you to listen for events triggered by the custom element, while event emitters enable the custom element to emit events that can be handled by parent components.