@dannymoerkerke/custom-element
v1.0.0
Published
Web Components base class which provides data binding and convenience methods
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Custom Element
A base class for Custom Elements which provides simple data binding.
This is a simple POC to demonstrate how data binding can be easily implemented using Web Components. It is not a replacement for React or other frameworks, nor is it intended to be.
See my article on medium.com for an in depth explanation.
How it works
Inside the Shadow Root of any Web Component that extends CustomElement
data binding can be provided through the data-bind
attribute on any HTML element, including other Web Components. Data binding is done through the properties of the state
object
inside CustomElement
.
For example:
<p data-bind="title"></p>
means the value of the state.title
property of CustomElement
is bound to this <p>
. If the value of state.title
changes the textContent
of this <p>
will change with it.
If the value of state.title
needs to be bound to a property of another Web Component it should be prefixed with the name
of that property and a :
.
For example:
<web-component data-bind="name:title"></web-component>
means the property name
of <web-component>
is bound to state.title
.
If <web-component>
also extends CustomElement
then its property state.name
is bound to state.title
, which allows
for multiple levels of data binding. This is because internally the setState
method of <web-component>
will be invoked.
CustomElement
also provides some convenience methods:
show(elements?: HTMLElement[])
, show the element itself or multiple child elements whenelements
argument is givenhide(elements?: HTMLElement[])
, hide the element itself or multiple child elements whenelements
argument is givenselect(selector: string)
, select an element from the component's Shadow DOM (callsquerySelector
internally)selectAll(selector: string)
, select multiple elements from the component's Shadow DOM (callsquerySelectorAll
internally)css(elements: HTMLElement | HTMLElement[], styles: Object)
, set multiple styles on one element or an array of elements at onceaddTemplate(element: HTMLElement, selector: string, replaceContents = false)
: add the contents of the<template>
which is selected byselector
toelement
. WhenreplaceContents
istrue
the existing contents ofelement
will be replaced.
This only works for templates inside the shadowRoot of the component
Example:
const container = this.shadowRoot.querySelector('#container');
this.css(container, {
display: 'flex'
paddingBottom: '10px',
backgroundColor: '#ff0000'
});
multiSelect({property: selector})
, selects an element in Shadow DOM and sets it to a property on the element
Example:
this.multiSelect({
container: '#container',
header: 'h1'
});
is equivalent to:
this.container = this.shadowRoot.querySelector('#container');
this.header = this.shadowRoot.querySelector('h1');
addTemplate(element: HTMLElement, selector: string, replaceContents?: boolean)
, adds the template selected byselector
to the element, optionally replacing existing content so the added template will be the only child
Demo
To run the demo, run npm install
once and then npm start
and view the demo on
http://localhost:8080/
Testing
Run npm test
and view the results on http://localhost:8080/
or run npm run test:headless
to run the tests on the command line.
This repo also contains the configuration file wallaby.js
to run the
tests from your IDE using Wallaby.js
Browser support
- Chrome 53+
- Firefox 63+
- Safari 10+
- iOS Safari 10+
- Chrome Android 71+
- Firefox Android 64+