Gutenberg hello world

myblock.js

var el = wp.element.createElement,
    registerBlockType = wp.blocks.registerBlockType,
    withAPIData = wp.components.withAPIData;

registerBlockType( 'sandbox/myblock', {
    title: 'My Block',
    icon: 'archive',
    category: 'widgets',
    
    // representation of the block in the editor's context
    edit: function( props ) {	    
        return el(
            'div', 
            {},
            "This is the editors content." 
        );
    },
    
    // content to save to databse, use on front end
    save: function() {
        return "This is the saved front-end HTML content."; // which can use PHP output with proper filters
    },
} );

myblock.php

<?php
add_action( 'enqueue_block_editor_assets', function () {
	wp_enqueue_script(
		'sandbox_myblock',
		plugins_url( 'myblock.js', __FILE__ ),
		array( 'wp-blocks', 'wp-i18n', 'wp-element' ),
		filemtime( plugin_dir_path( __FILE__ ) . 'myblock.js' ) 
	);
});