> **>>> TL;DR:** This provides a minimal vanilla JS base class that aims to reduce the complexity of creating reactive custom elements. See the [Quick Start Example](#quick-start-example)
Web Component Base
---
[](https://www.npmjs.com/package/web-component-base)
[](https://www.npmjs.com/package/web-component-base)
[](https://www.npmjs.com/package/web-component-base)
When you extend the `WebComponent` class for your component, you only have to define the `template` and `properties`. Any change in any property value will automatically cause just the component UI to render.
The result is a reactive UI on property changes.
## Table of Contents
1. [Import via unpkg](#import-via-unpkg)
1. [Installation via npm](#installation-via-npm)
1. [Usage](#usage)
1. [`template` vs `render()`](#template-vs-render)
1. [Quick Start Example](#quick-start-example)
1. [Life-Cycle Hooks](#life-cycle-hooks)
1. [`onInit`](#oninit) - the component is connected to the DOM, before view is initialized
1. [`afterViewInit`](#afterviewinit) - after the view is first initialized
1. [`onDestroy`](#ondestroy) - the component is disconnected from the DOM
1. [`onChanges`](#onchanges) - every time an attribute value changes
## Import via unpkg
Import using [unpkg](https://unpkg.com/web-component-base) in your vanilla JS component. We will use this in the rest of our [usage examples](#usage).
```js
import WebComponent from "https://unpkg.com/web-component-base/index.js";
```
## Installation via npm
Usable for projects using typescript, or with bundlers, or using import maps.
```bash
npm i web-component-base
```
## Usage
In your component class:
```js
// HelloWorld.mjs
import WebComponent from "https://unpkg.com/web-component-base/index.js";
class HelloWorld extends WebComponent {
name = "World";
emotion = "excited";
static properties = ["name", "emotion"];
get template() {
return `
Hello ${this.name}${this.emotion === "sad" ? ". ðŸ˜" : "! 🙌"}
`;
}
}
customElements.define('hello-world', HelloWorld);
```
In your HTML page:
```html
```
The result is a reactive UI that updates on attribute changes:
## `template` vs `render()`
This mental model attempts to reduce the cognitive complexity of authoring components:
1. The `template` is a read-only property (initialized with a `get` keyword) that represents *how* the component view is rendered.
1. There is a `render()` method that triggers a view render.
1. This `render()` method is *automatically* called under the hood every time an attribute value changed.
1. You can *optionally* call this `render()` method at any point to trigger a render if you need.
## Quick Start Example
Here is an example of using a custom element in a single .html file:
```html
WC Base Test
```
## Life-Cycle Hooks
Define behavior when certain events in the component's life cycle is triggered by providing hook methods
### onInit()
- Triggered when the component is connected to the DOM
- Best for setting up the component
```js
import WebComponent from "https://unpkg.com/web-component-base/index.js";
class ClickableText extends WebComponent {
// gets called when the component is used in an HTML document
onInit() {
this.onclick = () => console.log(">>> click!");
}
get template() {
return `Click me!`;
}
}
```
### afterViewInit()
- Triggered after the view is first initialized
```js
class ClickableText extends WebComponent {
// gets called when the component's innerHTML is first filled
afterViewInit() {
const footer = this.querySelector('footer');
// do stuff to footer after view is initialized
}
get template() {
return ``;
}
}
```
### onDestroy()
- Triggered when the component is disconnected from the DOM
- best for undoing any setup done in `onInit()`
```js
import WebComponent from "https://unpkg.com/web-component-base/index.js";
class ClickableText extends WebComponent {
clickCallback() {
console.log(">>> click!");
}
onInit() {
this.onclick = this.clickCallback;
}
onDestroy() {
console.log(">>> removing event listener");
this.removeEventListener("click", this.clickCallback);
}
get template() {
return `Click me!`;
}
}
```
### onChanges()
- Triggered when an attribute value changed
```js
import WebComponent from "https://unpkg.com/web-component-base/index.js";
class ClickableText extends WebComponent {
// gets called when an attribute value changes
onChanges(changes) {
const {property, previousValue, currentValue} = changes;
console.log('>>> ', {property, previousValue, currentValue})
}
get template() {
return `Click me!`;
}
}
```