JavaScript node

JavaScript Node

Overview

The JavaScript Node executes custom JavaScript against the pipeline payload and returns the result on a single result output port. It is ideal for ad-hoc transformations, quick calculations, and bridging logic gaps when purpose-built nodes are unavailable. The node injects pipeline context variables, runs the user script inside the Maestro engine, and wraps the return value in a consistent structure for downstream nodes.

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Core Functionality

1. Inline JavaScript Execution

• Author arbitrary ES5/ES6-compatible JavaScript directly inside the node.
• Access pipeline context variables such as $node, $trigger, $execution, and more.
• Return any JSON-serializable value (objects, arrays, scalars) via a return statement.

2. Context Injection

• $node['NodeName']: Outputs from any upstream node, keyed by node name or ID (recommended way to access data).
• $trigger: The original trigger data that started the execution.
• $input: Array of direct predecessor outputs (use $input[0] for the first predecessor).
• $item / $index: Current item and index when executing inside a For Each loop.
• $execution: Execution metadata (id, pipelineId, pipelineName, etc.).

3. Auto-Wrapped Output

• Result is emitted through defaultOut under the result field.
• Downstream nodes receive payloads shaped as { "result": <return value> }.
• Access outputs from downstream nodes via $node['JavaScript'].result.

4. Standard Settings

• Shares baseline retry and error handling controls with other nodes.
• Documentation settings let you annotate the purpose of the script on the pipeline canvas.

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Configuration Reference

Parameters

Parameter	Type	Default	Required	Description
Code	string (JS)	""	Yes	JavaScript code. Simple expressions are auto-returned; for multi-line logic use explicit return.

Available variables: $node["NodeName"], $trigger, $execution

Settings

Setting	Options	Default	Description
Timeout (seconds)	number	Pipeline default	Maximum execution time for this node (1--600).
Retry on Timeout	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry on timeout.
Retry on Fail	Pipeline Default / Enabled / Disabled	Pipeline Default	Whether to retry on failure. When Enabled, shows Advanced Retry Configuration.
On Error	Pipeline Default / Stop Pipeline / Continue Execution	Pipeline Default	Behavior when node fails after all retries.

Advanced Retry Configuration (only visible when Retry on Fail = Enabled):

Field	Type	Default	Range	Description
Max Attempts	number	3	1--10	Maximum retry attempts.
Initial Delay (ms)	number	1000	100--30,000	Wait before first retry.
Max Delay (ms)	number	120000	1,000--300,000	Upper bound for backoff delay.
Multiplier	number	2.0	1.0--5.0	Exponential backoff multiplier.
Jitter Factor	number	0.1	0--0.5	Random jitter.

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Usage Examples

Example 1: Format Operator Summary

Field	Value
Script	See snippet below
Notes	Build operator display name for dashboards.
Display Note in Pipeline	true

const operator = $node['Fetch Operator'].operator;
return {
  id: operator.badgeId,
  name: `${operator.firstName} ${operator.lastName}`.trim(),
  activeShift: operator.shift
};

The downstream payload exposes the formatted object under result (access via $node['Format Operator'].result).

Example 2: Calculate Production Yield

Field	Value
Script	See snippet below
On Error	Continue Execution

const data = $node['Read Production'];
const produced = Number(data.goodUnits || 0);
const defective = Number(data.scrapUnits || 0);
const total = produced + defective;
if (!total) {
  return { yield: 0 };
}
return { yield: Number(((produced / total) * 100).toFixed(2)) };

Even if the script throws, the Continue Execution setting lets the branch proceed for monitoring.

Example 3: Summarize Packaging Batch Metrics

Field	Value
Script	See snippet below
On Error	retryNode
Notes	Create aggregated stats for the current packaging batch.

const batch = $node['Read Batch'];
const cartons = Array.isArray(batch.cartons) ? batch.cartons : [];
const totalWeight = cartons.reduce((sum, carton) => sum + (carton.weightKg || 0), 0);
const defectiveCount = cartons.filter(carton => carton.defectFlag === true).length;
return {
  batchId: batch.batchId,
  cartonCount: cartons.length,
  averageWeightKg: cartons.length ? Number((totalWeight / cartons.length).toFixed(2)) : 0,
  defectiveCount
};

Use this when a packaging station sends per-carton details and you need a single summary object for downstream reporting.