innerBlocksDemo.js

( function(
	blocks,
	blockEditor,
	element,
) {
	var el = element.createElement;
	var InnerBlocks = blockEditor.InnerBlocks;
	blocks.registerBlockType( 'demo/inner-blocks', {
		title: 'Inner Blocks Demo',
		category: 'common',
		attributes: {},
		edit: function( props ) {
			return el(
				'div',
				{},
				'Before the inner block:',
				el( 'div', { style: { border: '2px solid red' }  }, el( InnerBlocks ) ), 
				'After the inner block:'
			);
		},
		save: function( props ) {
            return el(
				'div',
				{},
				'Before the inner block:',
				el( 'div', { style: { border: '2px solid red' }  }, el( InnerBlocks.Content ) ), 
				'After the inner block:'
			);
		},
	} )
} ) (
	window.wp.blocks,
	window.wp.blockEditor,
	window.wp.element,
);