ssh-edit/blocks/offcanvas-menu/index.js

const { registerBlockType } = wp.blocks;
const { createElement } = wp.element;

registerBlockType('srh/offcanvas-menu', {
    edit: function() {
        return createElement('div', { className: 'wp-block-srh-offcanvas-menu' },
            createElement('button', {
                className: 'hamburger-toggle',
                'aria-label': 'Toggle Menu'
            },
                createElement('span', {}),
                createElement('span', {}),
                createElement('span', {})
            ),
            createElement('div', { className: 'offcanvas-menu' },
                createElement('div', { className: 'offcanvas-menu-inner' },
                    createElement('p', {}, 'Menu will appear here on frontend')
                )
            )
        );
    },
    
    save: () => null
});