(cellId)) return;
            
            const editor = CodeMirror.fromTextArea(textarea, {
                mode: 'javascript',
                theme: document.body.dataset.theme === 'dark' ? 'material-darker' : 'default',
                lineNumbers: true,
                lineWrapping: true,
                indentUnit: 4,
                indentWithTabs: false,
                extraKeys: {
                    'Shift-Enter': () => runCellAndSelectBelow(cellId),
                    'Ctrl-Enter': () => runCe