What is the mandatory return format for an n8n Code node?

You must always return an array of objects where each object contains a 'json' property, for example: return [{json: { key: value }}].

How do I access webhook data correctly in n8n JavaScript?

Webhook data is nested under the 'body' property. Use $json.body.property or $input.first().json.body.property to access your data.

Which execution mode should I use for my n8n Code node?

Use 'Run Once for All Items' for 95% of use cases, as it is faster and allows you to perform aggregations, filtering, and batch processing across the entire dataset.

How do I reference data from a specific previous node?

Use the $node syntax, for example: $node["Node Name"].json, to access data from a specific point in your workflow regardless of the current input.

Are there built-in libraries available in the n8n Code node?

Yes, you have native access to Luxon (DateTime) for date manipulation, $jmespath for JSON querying, and $helpers.httpRequest for making API calls.

n8n JavaScript Code Expert

Name: n8n JavaScript Code Expert
Author: czlonkowski

byczlonkowski

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1,245

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Productivity & Workflow

Writes production-grade JavaScript for n8n Code nodes with precision data access and error handling.

This skill equips Claude with specialized knowledge for architecting, writing, and debugging JavaScript within n8n workflow Code nodes. It provides expert guidance on n8n-specific syntax like $input, $json, and $node, while ensuring compliance with the platform's unique data structure requirements. Whether you are performing complex data transformations, managing date-time logic with Luxon, or orchestrating API calls via built-in helpers, this skill ensures your scripts are optimized for the correct execution mode and return the mandatory array-of-objects format required for seamless workflow execution.

Key Features

01Optimizes scripts for 'Run Once for All Items' versus 'Run Once for Each Item' modes.

02Enforces the mandatory [{json: {...}}] return structure to prevent workflow failures.

03Provides patterns for accessing nested data structures, including specific Webhook body nesting.

04Includes deep integration knowledge for built-in helpers like Luxon (DateTime) and HTTP requests.

05Identifies and prevents common logic errors like missing return statements or incorrect expression syntax.

061,245 GitHub stars

Use Cases

01Standardizing date and time formats across different time zones using the built-in Luxon library.

02Creating custom logic to merge and filter data from multiple upstream nodes into a single consolidated output.

03Building complex data aggregations and transformations that require advanced array methods like map, filter, and reduce.

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add czlonkowski/n8n-skills n8n-code-javascript

For use in Claude.ai and ChatGPT

Download Skill