n8n-code-javascript

1# JavaScript Code Node
2 
3Expert guidance for writing JavaScript code in n8n Code nodes.
4 
5---
6 
7## Before you write a Code node
8 
9A new Code node has to pass this gate first:
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111. **Is there a native node for the job?** Check the job-to-node table in `using-n8n-mcp-skills`: Filter, IF / Switch,
12   Summarize, Aggregate, Split Out, Merge, Compare Datasets, Remove Duplicates, Sort + Limit, Date & Time, XML / HTML /
13   Extract From File / Convert To File, HTTP Request (pagination, batching) and Crypto cover most reaches for Code.
14   Their configs are in `n8n-node-configuration` → NATIVE_NODES.md.
152. **Would a short expression in that node do?** One expression, no function body — the helper methods (`.pluck()`,
16   `.sum()`, `.unique()`, `$ifEmpty()`, `.diffTo()`) are in `n8n-expression-syntax` and, on n8n-mcp 2.97.0+, in
17   `tools_documentation({topic: "expression_helpers"})`. Several statements inside `{{ }}` count as code, so they belong
18   here rather than in an Edit Fields field.
193. **Is the job on the closed list?** Loops or recursion no node expresses, state across runs
20   (`$getWorkflowStaticData`), parsing no node handles, an allowlisted library, heavy all-items work (thousands of items,
21   stated or measured), or one short Code node (~15 lines) replacing 4+ glue nodes that only reshape data.
22 
23If it passes, write the Code node and give it a note, so the next reader (and the review hooks) can see why:
24 
25```json
26…