n8n Code JavaScript
Writes and debugs JavaScript in n8n Code nodes when no native node fits.
Install
npx skills add czlonkowski/n8n-skills --skill n8n-code-javascript -g -a claude-code -y- Repository
- czlonkowski/n8n-skills6.6k
- Category
- Engineering
- Updated
- 11d ago
- License
- MIT
- Context cost
- Mediumabout 3,000 tokens
- Runs scripts
- No, instructions only
What it does
Write, review, or debug JavaScript in an n8n Code node. Use when a Code node is already in the workflow (editing it, fixing an error, choosing its mode, making it faster), or when a new one is justified: no native node fits (check the job-to-node table in using-n8n-mcp-skills first) and the job is on the closed list, loops or recursion no node expresses, state across runs, parsing no node handles, an allowlisted library, heavy all-items work, or one short node replacing 4+ glue nodes. Covers $input/$json/$node in code, this.helpers, Luxon, SplitInBatches loops, cross-iteration data, pairedItem, per-item performance, and the \"Why Code:\" note. Filtering, totals, dedupe, sorting, joins, file formats and API paging have native nodes (Filter, Summarize, Remove Duplicates, Sort, Merge, Extract From File, HTTP Request): see n8n-node-configuration. EXCEPTION, for the AI-agent-callable Custom Code Tool (@n8n/n8n-nodes-langchain.toolCode), use n8n-code-tool; it has a different runtime contract.
JavaScript Code Node
Expert guidance for writing JavaScript code in n8n Code nodes.
Before you write a Code node
A new Code node has to pass this gate first:
- Is there a native node for the job? Check the job-to-node table in
using-n8n-mcp-skills: Filter, IF / Switch, Summarize, Aggregate, Split Out, Merge, Compare Datasets, Remove Duplicates, Sort + Limit, Date & Time, XML / HTML / Extract From File / Convert To File, HTTP Request (pagination, batching) and Crypto cover most reaches for Code. Their configs are inn8n-node-configuration→ NATIVE_NODES.md. - Would a short expression in that node do? One expression, no function body, the helper methods (
.pluck(),.sum(),.unique(),$ifEmpty(),.diffTo()) are inn8n-expression-syntaxand, on n8n-mcp 2.97.0+, intools_documentation({topic: "expression_helpers"}). Several statements inside{{ }}count as code, so they belong here rather than in an Edit Fields field. - Is the job on the closed list? Loops or recursion no node expresses, state across runs
(
$getWorkflowStaticData), parsing no node handles, an allowlisted library, heavy all-items work (thousands of items, stated or measured), or one short Code node (~15 lines) replacing 4+ glue nodes that only reshape data.
If it passes, write the Code node and give it a note, so the next reader (and the review hooks) can see why:
{ "name": "Flatten category tree", "type": "n8n-nodes-base.code", "notes": "Why Code: Split Out considered, the tree has arbitrary depth (recursion)", "notesInFlow": true }
Editing or debugging a Code node that is already there doesn't need the gate, but if the node does a native-node job, say so and offer the native replacement.
Quick Start
// Basic template for Code nodes
const items = $input.all();
