JSON Data Utility: Extract Key-Value Pairs by Index

## 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: ```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.