119 lines
3 KiB
Markdown
119 lines
3 KiB
Markdown
Web Component Base
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---
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This is a very minimal base class for creating reactive custom elements easily.
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When you extend the `WebComponent` class for your component, you only have to define the `template()` and `observedAttributes()`, and changes in any attribute value will automatically cause the UI to render.
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The result is a reactive UI on attribute changes.
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## Table of Contents
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1. [Vanilla JS import](#vanilla-js-import)
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1. [Installation](#installation)
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1. [Usage](#usage)
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1. [Life-Cycle Hooks](#life-cycle-hooks)
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1. [`onInit`](#oninit) - the component is connected to the DOM
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1. [`onChanges`](#onchanges) - an attribute value changed
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## Vanilla JS import
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Import using [unpkg](https://unpkg.com/web-component-base) in your component. We will use this in the rest of our [usage examples](#usage).
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```js
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import WebComponent from "https://unpkg.com/web-component-base";
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```
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## Installation
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If you have a bundler to help resolving imports:
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```bash
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npm i web-component-base
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```
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## Usage
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In your component class:
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```js
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// HelloWorld.mjs
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import WebComponent from "https://unpkg.com/web-component-base";
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class HelloWorld extends WebComponent {
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name = "World";
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emotion = "excited";
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static get observedAttributes() {
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return ["name", "emotion"];
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}
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get template() {
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return `
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<h1>Hello ${this.name}${this.emotion === "sad" ? ". 😭" : "! 🙌"}</h1>`;
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}
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}
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customElements.define('hello-world', HelloWorld);
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```
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In your HTML page:
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```html
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<head>
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<script type="module" src="HelloWorld.mjs"></script>
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</head>
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<body>
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<hello-world name="Ayo" emotion="sad">
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<script>
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const helloWorld = document.querySelector('hello-world');
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setTimeout(() => {
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helloWorld.setAttribute('emotion', 'excited');
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}, 2500)
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</script>
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</body>
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```
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The result is a reactive UI that updates on attribute changes:
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<img alt="UI showing feeling toward Web Components changing from SAD to EXCITED" src="https://git.sr.ht/~ayoayco/web-component-base/blob/main/assets/wc-base-demo.gif" width="400" />
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## Life-Cycle Hooks
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Define behavior when certain events in the component's life cycle is triggered by providing hook methods
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### onInit()
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- gets triggered when the component is connected to the DOM
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- best for setting up the component
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```js
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import WebComponent from "https://unpkg.com/web-component-base";
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class ClickableText extends WebComponent {
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// gets called when the component is used in an HTML document
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onInit() {
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this.onclick = () => console.log(">>> click!");
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}
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get template() {
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return `<span style="cursor:pointer">Click me!</span>`;
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}
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}
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```
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### onChanges()
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- gets triggered when an attribute value changed
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```js
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import WebComponent from "https://unpkg.com/web-component-base";
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class ClickableText extends WebComponent {
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// gets called when an attribute value changes
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onChanges({attr, prev, curr}) {
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console.log('>>> something changed', {attr, prev, curr})
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}
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get template() {
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return `<span style="cursor:pointer">Click me!</span>`;
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}
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}
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```
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