How can I create a custom Gutenberg block in WordPress?

<!-- BEGIN COPY / PASTE -->
    // JavaScript: Register a new block
    wp.blocks.registerBlockType('myplugin/custom-block', {
      title: 'Custom Block',
      icon: 'smiley',
      category: 'common',
      edit: function(props) {
        return wp.element.createElement('p', {}, 'Hello, World!');
      },
      save: function(props) {
        return wp.element.createElement('p', {}, 'Hello, World!');
      }
    });
    
    // PHP: Enqueue block scripts
    function myplugin_enqueue_block_editor_assets() {
      wp_enqueue_script(
        'myplugin-block',
        plugins_url('block.js', __FILE__),
        array('wp-blocks', 'wp-element')
      );
    }
    add_action('enqueue_block_editor_assets', 'myplugin_enqueue_block_editor_assets');
    <!-- END COPY / PASTE -->