Recursive Subarray Flattener with Classification Columns and Sortable Reverse Index

How it works

1. 1.Run the manual trigger to emit two fictional items containing nested subarrays
2. 2.Truly recursive flattening emits one row per element with source, classification, index and value; items without batch get source UNKNOWN
3. 3.An IF node routes empty-string values to a quarantined Set while valid rows pass a flattened Set
4. 4.A second path builds one manifest row of batch ids, stage-marked and appended via Merge
5. 5.A final Code node sorts rows stably, assigns row ids, keys blank values as (empty) and counts UNKNOWN-source rows

Use cases

• Flattening nested webhook payloads before resending
• Tracing any row back to its parent array and original position at any nesting depth
• Combining multiple branch outputs into one inspectable sortable report

Requirements

• No credentials required; fully local processing
• For production: replace the sample node with a Webhook output using the same schema (batch field as parent id)

Setup and testing in n8n

1. Import the JSON into n8n and click Execute Workflow
2. Verify a single final report with 9 sorted rows including R001 from batches.inner and a reverse index where the blank value appears under (empty)
3. Edge case: remove the batch field from one sample item and confirm source=UNKNOWN with unknown_source_rows=1 without failure

Service Value

Ready-made workflow template for automation delivery and service execution.