testwrite.js

const endpointUrl = "opc.tcp://192.168.249.31:4840";
const opcua = require("node-opcua");
const StatusCodes = opcua.StatusCodes;
const AttributeIds = opcua.AttributeIds;
const DataTypes = opcua.DataType;

let client;
let session;

async function CreateConnection(){

    const OPCUAClient = opcua.OPCUAClient;
    console.log('Trying to connect ...');
    client = new OPCUAClient({});
    
    await client.connect(endpointUrl);
    console.log('Connected!');
    
    session = await client.createSession({userName: "Davide", password: "davide"});
    let val = await session.read({nodeId: "ns=4;s=opctest1_Copy1"})
    console.log(val.value.value);
  
  let nodeToWrite = {
      nodeId: "ns=4;s=opctest1_Copy1",
      attributeIds: opcua.AttributeIds.Value,
      value: {
          value: {
          dataType: opcua.DataType.UInt16, 
          value: 1098
          }
      },
      statusCode: opcua.StatusCodes.Good // <==== 
  }
  let risultato = await session.write(nodeToWrite);
  console.log(risultato);
  
  val = await session.read({nodeId: "ns=4;s=opctest1_Copy1"})
  console.log(val.value.value)

    await client.closeSession(session,true);
    await client.disconnect(); 
};

CreateConnection();