Extract a key–value pair by index from JSON to fields in n8n

This template takes a JSON object and a row index and returns exactly one key–value pair at that index. It’s a handy helper when you only need a single entry from a structured JSON payload (e.g., picking one form field for downstream logic).

Who’s it for

• Makers who want a quick JSON picker without writing full parsing logic.
• Developers testing API payloads or building proofs of concept.
• Ops/analysts who need to pluck a single field for emails, documents or notifications.

How it works

1. Manual Trigger (When clicking ‘Test workflow’) starts the flow.
2. Set → Input JSON Node holds your sample payload with:
   • myData: an object of key → value pairs.
   • rowIndex: a 0‑based index indicating which pair to extract.
3. Code (Python) → Find Key‑Value Pair iterates myData and returns [key, value] at rowIndex as result.
4. Set → Key maps result[0] to a field named result.
5. Set → Value maps result[1] to a field named result[1].
6. The selected key and value are then available to any downstream nodes.

How to set up

1. Open the workflow and select Input JSON Node.
2. Replace the sample with your own JSON:

   {
     "myData": { "name": "Alice", "age": "30", "city": "Paris" },
     "rowIndex": "1"
   }
   

3. Click Execute Workflow. Check the Key and Value nodes for the outputs.

Requirements

• n8n running (cloud or self‑hosted).
• Code node (Python) enabled in your n8n version.
• Input payload structure:
  • myData: object with keys/values
  • rowIndex: integer (0‑based)

How to customize

• Pick by key name (instead of index): adjust the Python code to look up a specific key.
• Handle nested objects/arrays: walk or flatten the structure before selecting.
• Change output shape: return { "key": ..., "value": ... } or write directly to next‑node fields.
• Validate inputs: add checks for out‑of‑range rowIndex, non‑object myData, or empty objects.

Add‑ons

• Webhook intake: Replace Manual Trigger with a Webhook to accept live JSON.
• Schema guard: Add an If/Function step to ensure myData is an object and rowIndex is numeric.
• Audit log: Append the selected key/value to Google Sheets or a database.

Use Case Examples

• Pull one field from a large API response to include in an email.
• Extract a specific answer from a form submission for conditional routing.
• Read a configuration pair from a settings object to control a downstream step.

Common troubleshooting

| Issue | Possible Cause | Solution | |---|---|---| | “Index out of range” | rowIndex is larger than the number of keys | Use a valid 0‑based index; add a guard in the Code node to clamp or default. | | Wrong key returned | Object key order differs from expectations | Object key order isn’t guaranteed across sources—prefer pick by key name for reliability. | | Empty/invalid output | myData is not an object or is empty | Ensure myData is a flat object with at least one key. | | Python errors | Code node’s Python runtime not available | Enable Python in the Code node or convert the snippet to JavaScript. | | Value type mismatch | Value isn’t a string | Cast as needed in the Set node or normalize types in the Code node. |

Need Help?

If you’d like this to pick by key, handle nested JSON, accept data via Webhook or fully customized to your needs, write to us and we’ll adapt the template to your exact use case.