jsTransform Component: Script Transformer. This component is used to transform and process messages using JavaScript scripts. It can flexibly modify the content of msg, metadata, and msgType to achieve functions such as data transformation, format conversion, and data enrichment.

JavaScript scripts support ECMAScript 5.1(+) syntax specifications and some ES6 features, including async/await/Promise/let, etc. They also support calling Go custom functions to extend functionality. For more details, see udf.

Configuration

Field	Type	Description	Default Value
jsScript	string	JavaScript transformation script	None

• jsScript: The JavaScript transformation script used to process messages. This field serves as the function body of the following function:

  function Transform(msg, metadata, msgType, dataType) {
      ${jsScript}
  }
  

  Parameter Description:

  • msg: Message content
    • When dataType=JSON, it is of type jsonObject, and fields can be accessed using msg.field.
    • When dataType=BINARY, it is of type Uint8Array, and the byte array can be manipulated directly, such as accessing the first byte with msg[0].
    • For other dataTypes, it is of type string.
  • metadata: Message metadata, of type jsonObject.
  • msgType: Message type, of type string.
  • dataType: Message data type (JSON, TEXT, BINARY, etc.), which needs to be converted to a string using String(dataType).

  Return Value:

  • Must return an object containing the transformed msg, metadata, and msgType:

    return {
        'msg': msg,           // Transformed message content
        'metadata': metadata, // Transformed metadata
        'msgType': msgType,   // Transformed message type
        'dataType': dataType  // Optional: Transformed data type
    };
    

  • Supported data type conversions:
    • The message data type can be modified using the dataType field in the return value.
    • The msg field supports returning a byte array (JavaScript array) that will be automatically converted to binary data.

Note

1. Script execution has a timeout limit, which is configured through config.ScriptMaxExecutionTime.

Relation Type

• Success: The script executes successfully, and the transformed message is sent to the Success chain.
• Failure: The message is sent to the Failure chain in the following cases:
  • Script syntax error
  • Script execution exception
  • Script execution timeout
  • Incorrect return value format

Execution Result

The component transforms the message by executing the JavaScript script:

• It can modify the content of msg.
• It can modify/add metadata.
• It can modify msgType.
• It can modify dataType.
• The complete transformed message is passed to the next node.

Configuration Examples

Basic Data Transformation Example

  {
    "id": "s1",
    "type": "jsTransform",
    "name": "Transformation",
    "configuration": {
      "jsScript": "metadata['name']='test01';\n metadata['index']=11;\n msg['addField']='addValue1'; return {'msg':msg,'metadata':metadata,'msgType':msgType};"
    }
  }

Binary Data Processing Example

  {
    "id": "s2",
    "type": "jsTransform",
    "name": "Binary Transformation",
    "configuration": {
      "jsScript": "if (String(dataType) === 'BINARY') { var newBytes = new Uint8Array(msg.length + 4); newBytes[0] = 0xFF; newBytes[1] = 0xFE; newBytes[2] = 0xFD; newBytes[3] = 0xFC; for (var i = 0; i < msg.length; i++) { newBytes[i + 4] = msg[i]; } metadata['processed'] = 'true'; return {'msg': newBytes, 'metadata': metadata, 'msgType': msgType, 'dataType': 'BINARY'}; } return {'msg': msg, 'metadata': metadata, 'msgType': msgType};"
    }
  }

Data Type Conversion Example

  {
    "id": "s3",
    "type": "jsTransform", 
    "name": "Type Conversion",
    "configuration": {
      "jsScript": "var bytes = [72, 101, 108, 108, 111]; metadata['converted'] = 'text_to_binary'; return {'msg': bytes, 'metadata': metadata, 'msgType': msgType, 'dataType': 'BINARY'};"
    }
  }

JSON Data Enrichment Example

  {
    "id": "s4",
    "type": "jsTransform",
    "name": "JSON Data Enrichment",
    "configuration": {
      "jsScript": "if (String(dataType) === 'JSON') { msg.timestamp = new Date().toISOString(); msg.processedBy = 'RuleGo'; if (msg.temperature !== undefined) { msg.temperatureF = msg.temperature * 9/5 + 32; msg.status = msg.temperature > 25 ? 'hot' : 'normal'; } metadata['enhanced'] = 'true'; } return {'msg': msg, 'metadata': metadata, 'msgType': msgType};"
    }
  }

Binary Protocol Parsing Example

  {
    "id": "s5",
    "type": "jsTransform",
    "name": "Protocol Parsing",
    "configuration": {
      "jsScript": "if (String(dataType) === 'BINARY' && msg.length >= 8) { var deviceId = (msg[0] << 8) | msg[1]; var functionCode = (msg[2] << 8) | msg[3]; var dataLength = (msg[4] << 8) | msg[5]; var payload = Array.from(msg.slice(6)); var result = { deviceId: deviceId, functionCode: functionCode, dataLength: dataLength, payload: payload, parsedAt: new Date().toISOString() }; metadata['protocol'] = 'custom'; metadata['parsed'] = 'true'; return {'msg': result, 'metadata': metadata, 'msgType': 'PARSED_DATA', 'dataType': 'JSON'}; } return {'msg': msg, 'metadata': metadata, 'msgType': msgType};"
    }
  }

Text Log Parsing Example

  {
    "id": "s6",
    "type": "jsTransform",
    "name": "Log Parsing",
    "configuration": {
      "jsScript": "if (String(dataType) === 'TEXT') { var logPattern = /^(\\d{4}-\\d{2}-\\d{2} \\d{2}:\\d{2}:\\d{2}) \\[(\\w+)\\] (.+)$/; var match = msg.match(logPattern); if (match) { var parsed = { timestamp: match[1], level: match[2], message: match[3], source: 'application' }; metadata['logParsed'] = 'true'; return {'msg': parsed, 'metadata': metadata, 'msgType': 'LOG_ENTRY', 'dataType': 'JSON'}; } } return {'msg': msg, 'metadata': metadata, 'msgType': msgType};"
    }
  }

Binary Data Encryption Example

  {
    "id": "s7",
    "type": "jsTransform",
    "name": "Data Encryption",
    "configuration": {
      "jsScript": "if (String(dataType) === 'BINARY') { var encrypted = new Uint8Array(msg.length + 4); encrypted[0] = 0xAA; encrypted[1] = 0xBB; encrypted[2] = 0xCC; encrypted[3] = 0xDD; for (var i = 0; i < msg.length; i++) { encrypted[i + 4] = msg[i] ^ 0x55; } metadata['encrypted'] = 'true'; metadata['algorithm'] = 'xor'; return {'msg': encrypted, 'metadata': metadata, 'msgType': msgType, 'dataType': 'BINARY'}; } return {'msg': msg, 'metadata': metadata, 'msgType': msgType};"
    }
  }

Multi-Data Type Conversion Example

  {
    "id": "s8",
    "type": "jsTransform",
    "name": "Smart Transformation",
    "configuration": {
      "jsScript": "var dt = String(dataType); metadata.originalType = dt; if (dt === 'JSON') { msg.converted = true; msg.convertedAt = new Date().toISOString(); return {'msg': msg, 'metadata': metadata, 'msgType': 'ENHANCED_JSON'}; } else if (dt === 'TEXT') { try { var parsed = JSON.parse(msg); metadata.textToJson = 'success'; return {'msg': parsed, 'metadata': metadata, 'msgType': 'CONVERTED_JSON', 'dataType': 'JSON'}; } catch(e) { metadata.conversionError = e.message; } } else if (dt === 'BINARY') { var hex = Array.from(msg).map(b => b.toString(16).padStart(2, '0')).join(''); metadata.hexString = hex; metadata.binaryLength = msg.length; } return {'msg': msg, 'metadata': metadata, 'msgType': msgType};"
    }
  }

Application Example

Transform the message and then execute subsequent logic.

{
  "ruleChain": {
    "id":"rule01",
    "name": "Test Rule Chain",
    "root": true
  },
  "metadata": {
    "nodes": [
       {
        "id": "s1",
        "type": "jsTransform",
        "name": "Transformation",
        "configuration": {
          "jsScript": "metadata['name']='test02';\n metadata['index']=22;\n msg['addField']='addValue2'; return {'msg':msg,'metadata':metadata,'msgType':msgType};"
        }
      },
      {
        "id": "s2",
        "type": "restApiCall",
        "name": "Push Data",
        "configuration": {
          "restEndpointUrlPattern": "<url id=\"d1d1j4gr7lpjqb3pt42g\" type=\"url\" status=\"failed\" title=\"\" wc=\"0\">http://192.168.136.26:9099/api/msg</url>   ",
          "requestMethod": "POST",
          "maxParallelRequestsCount": 200
        }
      }
    ],
    "connections": [
      {
        "fromId": "s1",
        "toId": "s2",
        "type": "Success"
      }
    ]
  }
}