Working with enhance in Aurelia 2: A Comprehensive Guide

Aurelia 2, a modern front-end JavaScript framework, introduces a powerful feature called enhance that allows developers to breathe life into static HTML by binding Aurelia behaviours to existing DOM elements. If you worked with Aurelia 1, you might already be familiar with enhance functionality. This isn’t a new feature added to Aurelia.

What is enhance in Aurelia 2?

The enhance function is a powerful feature of Aurelia 2 that provides a mechanism for developers to leverage the power of Aurelia within existing HTML pages. Essentially, it gives Aurelia the capability to enhance an existing DOM tree by associating Aurelia’s custom elements, custom attributes, or template controllers with the DOM nodes. This feature can be exceptionally useful in scenarios where a web page is partially server-rendered or when a DOM fragment needs to be added to the HTML document on the fly.

Enhancing Aurelia 2 within a React Application

Let’s dive into a real-world example where you’re working with Aurelia 2 inside another framework, such as React. Suppose you have an existing React application and want to add a new feature using Aurelia 2.

import { customElement, bindable } from 'aurelia';

@customElement('aurelia-counter')
export class AureliaCounter {
  @bindable count = 0;

  increment() {
    this.count++;
  }
}

This is a simple counter component with a count property and an increment method that increments the count. Now let’s see how we can use the enhance feature to integrate this Aurelia component into our existing React component:

import React, { useEffect } from 'react';
import Aurelia from 'aurelia';
import { AureliaCounter } from './aurelia-counter';

function App() {
  useEffect(() => {
    (async () => {
      const host = document.querySelector('#react-app');
      await Aurelia
        .register(AureliaCounter)
        .enhance({
          host,
          component: AureliaCounter,
        });
    })();
  }, []);

  return (
    

  );
}

export default App;

Enhancing Server-Rendered HTML in Multi-Page Applications

Consider a server-rendered multi-page application where we want to enhance a specific part of the page. Assume that the server generates HTML similar to the following:

...

  

    

...

The div with id static-content contains server-rendered static content. We have a DIV with an id of dynamic-content so we know which element is being enhanced. This setup allows you to combine the benefits of server-rendered HTML (fast initial page load) with Aurelia’s dynamic capabilities.

Let’s create an Aurelia component DynamicComponent:

import { customElement } from 'aurelia';

@customElement('dynamic-component')
export class DynamicComponent {
  // ...
}

And now, we can use enhance to inject the DynamicComponent into the dynamic-content div:

import Aurelia from 'aurelia';
import { DynamicComponent } from './dynamic-component';

(async () => {
  const dynamicContent = document.querySelector('#dynamic-content');

  await Aurelia
    .register(DynamicComponent)
    .enhance({
      host: dynamicContent,
      component: DynamicComponent,
    });
})().catch(console.error);

The advantage of this approach is that it reduces the client-side overhead by not making everything an Aurelia component. Only the parts of the page that need to be dynamic and interactive are enhanced with Aurelia, while the rest of the page remains static HTML rendered from the server. This way, you can achieve a balance between performance and interactivity.

In conclusion, enhance is a powerful tool in Aurelia 2’s arsenal, allowing developers to gradually adopt Aurelia 2, enhance existing HTML with Aurelia’s features, and even mix Aurelia with other libraries or frameworks. By understanding and using enhance, you can leverage the power and flexibility of Aurelia 2 while maintaining compatibility with existing code or frameworks.