ssh-edit/js/offcanvas-menu-editor.js

(function(blocks, element) {
    var el = element.createElement;
    
    blocks.registerBlockType('srh/offcanvas-menu', {
        edit: function() {
            return el('div', { className: 'wp-block-srh-offcanvas-menu' },
                el('button', { className: 'hamburger-toggle' },
                    el('div', { className: 'hamburger-lines' },
                        el('span'),
                        el('span'),
                        el('span')
                    ),
                    el('span', { className: 'menu-text' }, 'Menu')
                )
            );
        },
        save: function() {
            return null;
        }
    });
})(window.wp.blocks, window.wp.element);