Setup a Block as a Plugin

WordPress made a rad package that sets up webpack, Babel, and all the other packages we need to run React for WordPress Blocks.

Add a new folder in the plugins folder.

wp-content/plugins/josh-coast-banner-block

Create an index.php file in that folder.

<?php
/**
 * Plugin Name: Josh Coast Banner Block
 * Description: A banner intended for the top of a page including the page title and description.
 * Version: 1.0
 * Author: Josh Coast
 * Author URI: https://www.joshcoast.com/
 *
 * @package joshcoast
 **/

if( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly

class JoshCoastBannerBlock {
	function __construct() {
		add_action('init', array($this, 'adminAssets'));
	}

	function adminAssets() {
		register_block_type(__DIR__, array(
			'render_callback' => array($this, 'theHTML')
		));
	}

	function theHTML($attributes) {
		ob_start(); ?>
		<div class="josh-coast-banner-block"><pre style="display: none;"><?php echo wp_json_encode($attributes) ?></pre></div>
		<?php return ob_get_clean();
	}
}

$joshCoastBannerBlock = new JoshCoastBannerBlock();

Add a src directory. This directory will be where you work on all your source files. Webpack will build the files and place them all into your build directory for you. When telling WordPress where various files are, this build directory is where you will point to. 

wp-content/plugins/josh-coast-banner-block/src
wp-content/plugins/josh-coast-banner-block/build

Initialize npm to create the package.json file and run this with the terminal in your plugin directory.

npm init -y

Install the @wordpress/scripts

Run this with the terminal in your plugin directory.

npm install @wordpress/scripts --save-dev

Add the build and start lines ( lines 7 & 8 ) to your package.json file

{
  "name": "josh-coast-banner-block",
  "version": "1.0.0",
  "description": "",
  "main": "test.js",
  "scripts": {
    "build": "wp-scripts build",
    "start": "wp-scripts start",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@wordpress/scripts": "^26.2.0"
  }
}

To run these new scripts, run this with the terminal in your plugin directory.

npm run start // this runs the "watch" command for active development.
npm run build // this runs the "build" command for production.

This will create/update a build directory in your plugin!