change

Overview

The change node modifies message properties without writing code. Set values, change existing properties, delete unwanted data, or move properties around. Supports JSONata expressions for complex transformations.

Properties

Operations

// Set msg.payload to "hello"
// Set msg.topic to flow.device_id
// Set msg.timestamp to $now()

// Change "temp" to "temperature"
// Replace regex /\s+/g with " "
// Change "," to "." in payload

// Delete msg.password
// Delete msg._private
// Delete msg.payload.debug

// Move msg.data to msg.payload
// Move msg.temp to msg.sensors.temperature
// Move msg.raw to msg._backup

Value Types

Example: Sensor Data Normalization

Transform raw sensor data into a standardized format.

// Change node rules:
[
  // Move raw value to payload.raw
  { "t": "move", "p": "payload", "to": "payload.raw" },

  // Set normalized structure
  { "t": "set", "p": "payload.value", "to": "payload.raw.reading", "tot": "msg" },
  { "t": "set", "p": "payload.unit", "to": "°C", "tot": "str" },
  { "t": "set", "p": "payload.deviceId", "to": "device_001", "tot": "flow" },

  // Add timestamp using JSONata
  { "t": "set", "p": "payload.timestamp", "to": "$now()", "tot": "jsonata" },

  // Delete sensitive data
  { "t": "delete", "p": "payload.raw.apiKey" }
]

Example: JSONata Transformations

Use JSONata for complex data transformations.

// JSONata expressions in change node:

// Calculate average of array
{ "t": "set", "p": "payload.average",
  "to": "$average(payload.readings)", "tot": "jsonata" }

// Format date
{ "t": "set", "p": "payload.dateFormatted",
  "to": "$fromMillis($now(), '[Y]-[M01]-[D01]')", "tot": "jsonata" }

// Filter and transform array
{ "t": "set", "p": "payload.activeDevices",
  "to": "payload.devices[status='active'].{\"id\": id, \"name\": name}",
  "tot": "jsonata" }

// Conditional value
{ "t": "set", "p": "payload.status",
  "to": "payload.temperature > 30 ? 'hot' : 'normal'", "tot": "jsonata" }

Common Patterns

Set msg.timestamp
to: $now()
type: jsonata

Move msg.temp
to: msg.temperature

Set msg.payload.source
to: msg.topic
type: msg

Delete msg.payload.password
Delete msg.payload.token
Delete msg.payload.apiKey