dom-controller
v0.4.4
Published
Adds controller logic to elements through attributes
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hedzerReadme
dom-controller
Attach behavior to any element in a clear and debuggable way.
Less than 2KB minified + zipped
Example Usage
<!-- index.html -->
<head>
<!-- include the library -->
<script src="https://unpkg.com/[email protected]/bundle.min.js" defer></script>
<!-- reference the controller -->
<link controller-name="fancy" href="/controllers/to-do/fancy.mjs" />
</head>
<body>
<!-- controller will attach to this ul -->
<ul controller="fancy">
<li>Caviar</li>
<li>Champagne</li>
</ul>
</body>// controllers/to-do/fancy.mjs
export default class FancyController {
// called when [controller="fancy"] is set
async attach(element) {
add_save_events(element);
load_items(element);
}
// called when [controller] is changed or removed
async detach(element) {
cancel_load_items(element);
remove_save_events(element);
}
}You can also use TypeScript.
// controllers/to-do/fancy.ts
import { IController } from 'dom-controller/IController';
export default class FancyController implements IController<HTMLElement> {
element!: HTMLElement;
async attach(element: HTMLElement): Promise<void> { }
async detach(element: HTMLElement): Promise<void> { }
}Lifecycle calls
attach() is called when a controller is attached to an element. i.e. When the controller attribute is set to the name of a controller.
detach() is called when a controller is detached. This happens when an element is removed or when the controller attribute is changed to something new.
Load as module
Sometimes you need a .js to act like .mjs. To do this add type-is="module"
example:
<link
type-is="module"
controller-name="fancy"
href="/controllers/to-do/fancy.js"
/>Using preload
Preload will tell your browser to load the scripts in advance. This is especially useful if you add immutable headers & a cache busting parameter.
<link
type-is="module"
controller-name="fancy"
href="/controllers/to-do/fancy.js"
rel="preload" as="script"
crossOrigin="anonymous"
/>Old-school loading, in order
<!-- index.html -->
<head>
<!-- include the library -->
<script src="https://unpkg.com/[email protected]/bundle.min.js" defer></script>
<!-- reference the controller -->
<!-- it must come after loading dom-controller.js -->
<script src="/controllers/to-do/fancy.js" defer></script>
</head>
<body>
<!-- controller will attach to this ul -->
<ul controller="fancy">
<li>Caviar</li>
<li>Champagne</li>
</ul>
</body>// controllers/to-do/fancy.js
class FancyController {
async attach(element) { }
async detach(element) { }
}
DomController.registerController(FancyController, 'fancy');// controllers/to-do/fancy.ts
import { IController } from 'dom-controller/IController';
class FancyController implements IController<HTMLElement> {
element!: HTMLElement;
async attach(element: HTMLElement): Promise<void> { }
async detach(element: HTMLElement): Promise<void> { }
}
// @ts-ignore
DomController.registerController(FancyController, 'fancy');Script Placement
If you are using modules, i.e. *.mjs/import/export default, and loading using a link controller alias, then the dom-controller.js script can be loaded anytime anywhere.
If you aren't using modules, or you're using the window.DomController.registerController() call then the library needs to be loaded before any controller. You can speed up loading by using the defer attribute <script defer ...>.
Decoupling
Here's how you can efficiently reuse a controller for multiple related elements. Elements keep internal state and produce events, controllers talk to the server and update element data.
// interfaces/todo-element.ts
export interface TodoElement extends HTMLUListElement {
add(item: Item): void;
remove(id: string): void;
}// elements/basic-todo.ts
import { TodoElement } from 'interfaces/todo-element.ts';
class BasicTodo implements TodoElement extends HTMLUListElement {
constructor() {...}
add(item: Item): void { }
remove(id: string): void { }
}
window.customElements.define('basic-todo', BasicTodo);// elements/premium-todo.ts
import { TodoElement } from 'interfaces/todo-element.ts';
class PremiumTodo implements TodoElement extends HTMLUListElement {
constructor() {...}
add(item: Item): void { }
remove(id: string): void { }
}
window.customElements.define('premium-todo', PremiumTodo);// controllers/todo.ts
import { IController } from 'dom-controller/IController';
import { TodoElement } from 'interfaces/todo-element.ts';
export default class TodoController implements IController<TodoElement> {
element!: TodoElement;
async attach(element: TodoElement): Promise<void> {
element.add({ id: 1, text: 'Tada 🎉' })
}
async detach(element: TodoElement): Promise<void> { }
}
<!-- index.html -->
<head>
<!-- include the library -->
<script src="https://unpkg.com/[email protected]/bundle.min.js" defer></script>
<!-- reference the controller -->
<link
type-is="module"
controller-name="todo"
href="/controllers/todo.js"
/>
</head>
<body>
<basic-todo controller="todo">
<li>Cheez Wiz</li>
<li>Grape Soda</li>
</basic-todo>
<premium-todo controller="todo">
<li>Caviar</li>
<li>Champagne</li>
</premium-todo>
</body>Pros:
- Helps track breaking changes.
- Intellisense works well.
- Interfaces don't add to transpiled size, they are "free".
- Code reuse / DRY.
Cons:
- Increased complexity, don't use unless you need it.