var myImports = new JavaImporter(java.io, java.lang, java.util,java.lang.Object, org.mycontroller.standalone.utils.McUtils);

with(myImports) {
  var options = new HashMap();
  options.put("orderBy", "Eui");
  options.put("order", "asc");
  options.put("pageLimit", new Long(-1)); // -1 to list all the nodes

  var nodes = mcApi.node().getAll(options);

  var nodesVar = mcApi.variable().get("nodes_state"); // It is good to have key in lowercase and no space
  var nodesOU = JSON.parse(nodesVar.value);
  var nodesOD = JSON.parse(nodesVar.value2);

  var nodesU = [];
  var nodesD = [];

  var subject = "[MyController] Nodes status";
  var tableBody = "";

  for (i = 0; i < nodes.data.length; i++) {

    var nodeStatus = { };
    var _nodeId = nodes.data[i].getId(); // nodeId is unique and internal
    // but still if you want to refer node EUI and gateway id, use the following line and comment above line.
    //var _nodeId = nodes.data[i].getGatewayTable().getId() + '-' + nodes.data[i].getEui();
    var _nodeState = nodes.data[i].getState();
    
    nodeStatus[_nodeId] = _nodeState; // update in to our common map

    if (_nodeState == "UP") {
      nodesU.push(_nodeId);
      var prevState = "";
      for (j = 0; j < nodesOU.length; j++){
        if (nodesOU[j] == _nodeId) prevState = "UP";
      }
      if (prevState != "UP")
        tableBody += "<tr style='color: green;'><td>" + _nodeId + "</td><td>" + nodes.data[i].getName() + "</td><td>" + nodes.data[i].getEui() + "</td><td>" + _nodeState + "</td><td>" + mcApi.utils().friendlyTime(nodes.data[i].getLastSeen()) + "</td></tr>";
    }

    if (_nodeState == "DOWN") {
      nodesD.push(_nodeId);
      var prevState = "";
      for (j = 0; j < nodesOD.length; j++){
        if (nodesOD[j] == nodeId) prevState = "DOWN";
      }
      if (prevState != "DOWN")
        tableBody += "<tr style='color: red;'><td>" + _nodeId + "</td><td>" + nodes.data[i].getName() + "</td><td>" + nodes.data[i].getEui() + "</td><td>" + _nodeState + "</td><td>" + mcApi.utils().friendlyTime(nodes.data[i].getLastSeen()) + "</td></tr>";
    }
  }
  
  if (tableBody.length > 0){
    var pageStart = "Hello,<BR><BR>";
    var tableStyle = '<table border = "1" cellpadding = "5" style="border-collapse: collapse;border: none;"><tbody><tr><th align="left">Id</th><th align="left">Name</th><th align="left">EUI</th><th align="left">State</th><th align="left">Since</th></tr>';
    var tableEnd = '</tbody></table>';
    var pageEnd = "<BR><BR>--MyController.org<BR>";
    //  mcApi.operation().sendPushbulletNote(null, "abc@xyz.com", null, subject, message);
    mcApi.operation().sendEmail("abc@xyz.com", subject, pageStart + tableStyle + tableBody + tableEnd + pageEnd);
  }
    
  nodesVar.value = JSON.stringify(nodesU);
  nodesVar.value2 = JSON.stringify(nodesD);
  nodesVar.save();
}

Email will be looking like this,

I'm not a java programmer, so any suggestion on the code is more than welcome:

var myImports = new JavaImporter(java.io, java.lang, java.util,java.lang.Object, org.mycontroller.standalone.utils.McUtils);

with(myImports) {
	var options = new HashMap();
	options.put("orderBy", "Eui");
	options.put("order", "asc");
	options.put("pageLimit", new Long(-1)); // -1 to list all the nodes

	var nodes = mcApi.node().getAll(options);

	var nodesVar = mcApi.variable().get("Nodes state");
	var nodesOU = JSON.parse(nodesVar.value);
	var nodesOD = JSON.parse(nodesVar.value2);

	var nodesU = [];
	var nodesD = [];

	var subject = "[MyController] Nodes status";
	var messageU2D = "";
	var messageD2U = "";
	var message = "";

	for (i = 0; i < nodes.data.length; i++) {

		var nodeStatus = new Object();
		nodeStatus['key']   = nodes.data[i].getGatewayTable().getId() + '-' + nodes.data[i].getEui();
		nodeStatus['state'] = nodes.data[i].getState();

		if (nodeStatus['state'] == "UP") {
			nodesU.push(nodeStatus['key']);
			var prevState = "";
			for (j = 0; j < nodesOU.length; j++){
				if (nodesOU[j] == nodeStatus['key']) prevState = "UP";
			}
			if (prevState != "UP")
				messageD2U += nodes.data[i].getEui() + " : " + nodes.data[i].getName() + " : " + mcApi.utils().friendlyTime(nodes.data[i].getLastSeen()) + "<BR>";
		}

		if (nodeStatus['state'] == "DOWN") {
			nodesD.push(nodeStatus['key']);
			var prevState = "";
			for (j = 0; j < nodesOD.length; j++){
				if (nodesOD[j] == nodeStatus['key']) prevState = "DOWN";
			}
			if (prevState != "DOWN")
				messageU2D += nodes.data[i].getEui() + " : " + nodes.data[i].getName() + " : " + mcApi.utils().friendlyTime(nodes.data[i].getLastSeen()) + "<BR>";
		}

	}

	if (messageU2D != ""){
		message += "Nodes DOWN: <BR>";
		message += messageU2D;		
	}

	if (messageD2U != ""){
		message += "Nodes UP: <BR>";
		message += messageD2U;		
	}
	
	if (message != "")
		//  mcApi.operation().sendPushbulletNote(null, "abc@xyz.com", null, subject, message);
		mcApi.operation().sendEmail("abc@xyz.com", subject, message);

	nodesVar.value = JSON.stringify(nodesU);
	nodesVar.value2 = JSON.stringify(nodesD);
	nodesVar.save();
}

put("state", "Down");

I tried, but I still get the same error if I add this line to your script:

var nodes = mcApi.node().getAll(filters);```

  options.put("state", "Down");

I did some small script, Not complete!

var myImports = new JavaImporter(java.io, java.lang, java.util, java.text, java.util.HashMap);

with(myImports) {
  // filters
  var filters = new HashMap();
  filters.put("orderBy", "lastSeen");
  filters.put("order", "desc");
  filters.put("state", "Down");  
}

Let me know if you need a complete solution, like how to ignore duplicate, etc.,

  options.put("state", "DOWN");

but I receive the error:

  "errorMessage": "java.lang.String cannot be cast to java.lang.Enum"

I'm not a Java programmer, so I'm trying to understand how to use the HashMap looking at the examples I found on your forum.
It's surely a stupid error, but I cannot understand where it is...

Thank you for any help
Daniele