Run custom JavaScript code on each incoming payload to transform, calculate, or enrich data.
What It Does
The JavaScript Node lets you run custom JavaScript logic on each incoming payload. It provides full control to manipulate, transform, or enrich the data before passing it to downstream nodes.
Common use cases:
-
Conditional logic not supported by other nodes
-
Complex payload restructuring
-
Device-specific transformations
-
Timestamp formatting or encoding conversions
⚙️ Configuration Options
| Field | Required | Description |
|---|---|---|
| Node name | ✅ | Unique label to identify the node |
| JavaScript Templates | Optional | Choose from a list of ready-made snippets for common transformations |
| Add Device ID | Optional | Adds deviceId to the payload automatically as payload.deviceId |
| Description | Optional | Internal notes for documentation and maintenance |
| Error handling action | ✅ | What to do on script failure: - Continue – Add Error to JSON - Stop execution (block the payload) |
Step-by-Step: How to Configure the Node
1. Add the Node
Drag the JavaScript Node from the Logic & ETL group into your workflow.
2. Set the Node Name
Use a meaningful label (e.g., Normalize Format, Check Range, Hex Decode).
3. Use a JavaScript Snippet (Optional)
You can start with a predefined script from the Choose Snippet dropdown (see full list below).
4. Write or Customize the Code
Work directly on the payload object using standard JavaScript syntax. Return the updated payload at the end.
Example:
payload.tempC = (payload.tempF - 32) * (5 / 9);
return payload;
5. Add Device ID (Optional)
Enable this option to automatically add the current device’s ID to payload.deviceId.
6. Add Description (Optional)
Use this field to record purpose, expected input/output, or known edge cases.
7. Set Error Handling
Choose between:
-
Continue – Add Error to JSON: Payload continues with an
errorfield -
Stop: Node halts the payload flow on failure
Available Code Snippets (Predefined Scripts)
| Snippet Name | Description |
|---|---|
| Add UID | Adds UID from current context to the payload |
| Add Missing Field | Adds a default value if a key is missing |
| Convert Base64 to Hex | Decodes Base64 string to hex format |
| Convert Binary to Signed Decimal | Converts binary input into a signed integer |
| Convert Joules to kWh | Applies energy unit conversion |
| Delete Array Element | Removes a specific entry from an array |
| Epoch Time in ms Format | Converts timestamp to UNIX epoch in milliseconds |
| Field name has dash or spaces | Safely access fields with non-standard keys |
| Find Distance Between Two Lat/Long Points | Calculates geospatial distance |
| For Loop | Template for iterating over an array or values |
| If field does not exist - add it | Adds fallback field with default if missing |
| Last Element of Array | Extracts the last entry from an array |
| Loop Over Child Elements and Add Value | Applies a transformation across all children |
| Power Factor calculation | Calculates power factor using voltage/current/phase angle |
| Trim Fields from JSON | Removes unnecessary or sensitive fields |
You can insert a snippet and then modify it to fit your specific payload structure.
Example Configurations
Example 1: Capitalize Status
payload.status = payload.status.toUpperCase();
return payload;
Example 2: Add Device ID to Payload
Enable Add Device ID, or use manually:
payload.deviceId = '[[deviceId]]'; // if using template
return payload;
Example 3: Add Field If Missing
if (!payload.temperature) {
payload.temperature = 0;
}
return payload;
Q&A
Q: Do I always need to return the payload?
A: Yes. Without return payload;, downstream nodes won’t receive updated data.
Q: Can I use external libraries (e.g., lodash, moment)?
A: No. Only native JavaScript is supported in the sandbox.
Q: What happens if there's a runtime error?
A: The behavior depends on your selected error handling setting.
Q: Can I write multi-line or nested logic?
A: Yes — full JavaScript (ES5/ES6) is supported including loops, functions, if/else.