Browse an OPC UA address space in Node.js

The code

const { OPCUAClient, BrowseDirection, NodeClassMask, ResultMask } = require("node-opcua");

(async () => {
  const client = OPCUAClient.create({ endpointMustExist: false });
  await client.connect("opc.tcp://opcua.umati.app:4840");
  const session = await client.createSession();

  const result = await session.browse({
    nodeId: "ObjectsFolder",
    browseDirection: BrowseDirection.Forward,
    referenceTypeId: "HierarchicalReferences",
    includeSubtypes: true,
    nodeClassMask: NodeClassMask.Object | NodeClassMask.Variable,
    resultMask: ResultMask.BrowseName | ResultMask.NodeClass | ResultMask.TypeDefinition,
  });

  for (const ref of result.references) {
    console.log(ref.browseName.toString().padEnd(24),
                ref.nodeClass.toString().padEnd(10),
                ref.nodeId.toString());
  }

  await session.close();
  await client.disconnect();
})();

What it prints

Server                   Object     ns=0;i=85
Machines                 Object     ns=3;i=1001
DeviceSet                Object     ns=2;i=5001

Notes

• Filter with nodeClassMask and referenceTypeId in the request. Pulling every reference and filtering in JavaScript wastes a round trip and the server's continuation points.
• Request TypeDefinition in the resultMask. Seeing MachineToolType come back tells you immediately that this is a semantic integration rather than tag-scraping.
• If `result.continuationPoint` is set there is more to fetch: call browseNext, and release continuation points you abandon.
• `opcua-commander` gives you an interactive tree over SSH with no code, which is often what you actually want on a gateway.

What breaks first

Last verified 7 September 2026 against OPC UA 1.05.07. OPC UA Connect is an educational resource and is not affiliated with the OPC Foundation.