Custom Code Workflow Action in Sparkforge

By Sparkforge Support Team ·Last reviewed May 3, 2026

The Custom Code action runs JavaScript inside a workflow step. Map values from earlier steps as inputData, run your logic, and assign the result to output for downstream actions.

The Custom Code action lets a workflow execute JavaScript so you can extend logic past what built-in actions cover. Map values from previous steps as inputs, transform them, and return an object the rest of the workflow can read.

How to configure

  • Action Name: a label that says what the code does.
  • Language: JavaScript. No other languages are supported right now.
  • Property to Include in Code: add key-value pairs. The value can be hardcoded or pulled dynamically from a previous step. Reference each one in code as inputData.<key>. If the key is number1, you read it as inputData.number1.
  • Code: JavaScript that processes the inputs. The result must be assigned to output as a JavaScript object or array of objects.

Field reference

FieldDescriptionRequired
Action NameDisplay name of the step in the workflow.Yes
LanguageDefaults to JavaScript.Yes
Property To Include In CodeKeys mapped from earlier steps; access them via inputData.keyName.Yes
CodeJavaScript that produces the output object.Yes

Example

// Wrapped in an async function for you
const sum = inputData.number1 + inputData.number2;
output = { result: sum };

This adds two mapped numeric inputs and returns the sum on output.result, which downstream steps can reference.

Notes

  • Always assign the final value to output. A return statement alone is not enough.
  • If the result is missing or malformed, downstream steps that depend on it will fail or skip.
  • Keep the code small and deterministic. For long-running calls, use a webhook step instead.

Frequently Asked Questions

What languages does the Custom Code action support?
JavaScript only. No other runtimes are available at this time.
How do I read values from earlier workflow steps?
Add them under Property to Include in Code, then reference them as inputData.keyName in your script.
How do I return data to the next workflow step?
Assign your result to the output variable as an object or array of objects, e.g., output = { result: sum };.
Can I make external API calls from Custom Code?
For long-running or external HTTP work, the dedicated webhook action is a better fit. Custom Code is intended for in-line transforms.

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