@converse/skeletor

Skeletor

Skeletor is a Backbone fork that adds various improvements and features.

Introduction

The goal of Skeletor is to modernize Backbone and to allow you to stop writing imperative view code (e.g. manually adding and removing DOM nodes) and instead start writing declarative, component-based code that automatically updates only the changed parts of the DOM, similarly to basically all modern JavaScript frameworks.

The original Backbone Views aren't components can't be rendered in a nested and declarative way. Instead, it's up to you to manually make sure that these views are rendered in the correct place in the DOM. This approach becomes unwieldy, difficult and fragile as your site becomes larger and more complex.

Skeletor solves this by creating a new type of View, called ElementView, which is very similar to the original Backbone View but which is also a web component that gets instantiated automatically as soon as its rendered in the DOM.

Why bother?

The goal of this fork is to allow the Converse team to gradually update the Converse XMPP webchat client to use web components (using LitElement) without requiring us to put everything on hold in order to do a massive rewrite.

The end-goal is to not have any Skeletor Views at all, only LitElement components.

We can cheat a little by letting the existing Views also be web components (more accurately, "custom elements"), this allows us to declaratively render the UI, while we're progressively getting rid of the views.

Sekeletor adds the following changes to Backbone

• Removes the dependency on jQuery
• Instead of the render method Views can have a toHTML method which must return a lit-html TemplateResult.
• Replaces underscore with lodash
• Imports lodash methods individually to allow for tree-shaking
• Uses the native browser API instead of lodash whereever possible
• Drops support for older browsers (including IE) and uses ES6+ language features
• Splits models, views and collections into separate modules
• Adds the possibility to returns promises for asynchronous operations
• Adds a new ElementView class, which is a like a Backbone View, but doubles as an instance of HTMLElement and can be used to register a custom element or web-component.

Backwards incompatible changes

• Collection.prototype.forEach no longer returns the items being iterated over. If you need that, use map instead.
• The chain method on Models has been removed.
• The inject, foldl and foldr methods on Collections has been removed. You can use reduce instead.
• Removed the sample, take, tail and initial method on Collections.
• Removed the without, reject and select methods on Collections, use filter.

Changes due to using Lodash instead of Underscore

1. Use drop instead of rest.
2. indexBy is called keyBy
3. Use invokeMap for collections instead of invoke.
4. Use includes instead of contains
5. The partition and invokeMap methods have been removed.

ElementView example

The ElementView looks very similar to a normal Backbone View.

Since it's a web component, you need to call CustomElementRegistry.define to register it.

The this variable for the ElementView is the custom DOM element itself, in this case, <my-custom-button>.

So there is no el attribute and this.el will be undefined. Whereever in a Backbone View you'd use this.el, with an ElementView you'd just use this.

import { ElementView } from '@converse/skeletor/src/element.js';
import { render } from 'lit';
import { html } from 'lit';

export default class MyCustomButton extends ElementView {
    events = {
        'click .button': 'onButtonClicked'
    }

    async initialize () {
        this.model = new Model({ count: 0 });
        this.listenTo(this.model, 'change', this.render)
    }

    render () {
      return render(html`<button class="button">I've been clicked ${model.get('count')} times!</button>`, this);
    }

    onButtonClicked () {
      this.model.save('count', this.model.get('count')+1);
    }
}

CustomElementRegistry.define('my-custom-button', MyCustomButton);

You can now put your custom element in the DOM, and once the DOM is loaded by the browser, your ElementView will automatically be instantiated and initialize will be called.

  <div>
    <my-custom-button></my-custom-button>
  </div>