Task: Google Spreadsheet to HTML - Variant with JS Function

n8n workflow:
{"nodes":[{"name":"Read from Google Sheets","type":"n8n-nodes-base.googleSheets","position":[460,300],"parameters":{"options":{},"sheetId":"1uFISwZJ1rzkOnOSNocX-_n-ASSAznWGdpcPK3_KCvVo"},"credentials":{"googleSheetsOAuth2Api":{"id":"19","name":"Tom's Google Sheets account"}},"typeVersion":2},{"name":"Respond to Webhook","type":"n8n-nodes-base.respondToWebhook","position":[900,300],"parameters":{"options":{"responseHeaders":{"entries":[{"name":"Content-Type","value":"text/html; charset=UTF-8"}]}},"respondWith":"text","responseBody":"={{$json[\"html\"]}}"},"typeVersion":1},{"name":"Build HTML","type":"n8n-nodes-base.function","position":[680,300],"parameters":{"functionCode":"const columns = Object.keys(items[0].json);\n\nconst html = `\n<!doctype html>\n<html lang=\"en\">\n  <head>\n    <meta charset=\"utf-8\">\n    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">\n    <title>HTML Table Example</title>\n    <link href=\"https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/css/bootstrap.min.css\" rel=\"stylesheet\" integrity=\"sha384-gH2yIJqKdNHPEq0n4Mqa/HGKIhSkIHeL5AyhkYV8i59U5AR6csBvApHHNl/vI1Bx\" crossorigin=\"anonymous\">\n  </head>\n  <body>\n    <div class=\"container\">\n      <div class=\"row\">\n        <div class=\"col\">\n          <h1>HTML Table Example</h1>\n          <table class=\"table\">\n            <thead>\n              <tr>\n                ${columns.map(e => '<th scope=\"col\">' + e + '</th>').join('\\n')}\n              </tr>\n            </thead>\n            <tbody>\n              ${items.map(e => '<tr>' + columns.map(ee => '<td>' + e.json[ee] + '</td>').join('\\n') + '</tr>').join('\\n')}\n            </tbody>\n          </table>\n        </div>\n      </div>\n    </div>\n    <script src=\"https://cdn.jsdelivr.net/npm/bootstrap@5.2.0/dist/js/bootstrap.bundle.min.js\" integrity=\"sha384-A3rJD856KowSb7dwlZdYEkO39Gagi7vIsF0jrRAoQmDKKtQBHUuLZ9AsSv4jD4Xa\" crossorigin=\"anonymous\"></script>\n  </body>\n</html>\n`;\n\nreturn [{\n  json: {\n    html: html\n  }\n}];"},"typeVersion":1},{"name":"Webhook","type":"n8n-nodes-base.webhook","position":[240,300],"webhookId":"bbcd9487-54f9-449d-8246-49f3f61f44fc","parameters":{"path":"bbcd9487-54f9-449d-8246-49f3f61f44fc","options":{},"responseMode":"responseNode"},"typeVersion":1}],"connections":{"Webhook":{"main":[[{"node":"Read from Google Sheets","type":"main","index":0}]]},"Build HTML":{"main":[[{"node":"Respond to Webhook","type":"main","index":0}]]},"Read from Google Sheets":{"main":[[{"node":"Build HTML","type":"main","index":0}]]}}}