Null value when calling a recursive function in node.js

Question

I have this scenario I'm trying to map one JSON definition to another, I have a recursive function named find which works perfectly when I do simple operations but when I send complex conditions I always get a undefined value over the assigment.

  var mapToModel = function(res){
  var processes = res.definitions.process;
  var diagrams = res.definitions.BPMNDiagram; 
  var documents = [];
  for(var prop in processes) {
    if(processes.hasOwnProperty(prop)){
      var propertyNames = Object.getOwnPropertyNames(processes[prop]);
      for(var property in processes[prop]){
        var mapping ={};
        if(property==="$"){
          //do something with the process
        }else{
        //shapes
          console.log("\n");
          mapping.id = new mongo.ObjectID();
          mapping.hash = hash.hashCode(new Date().toString());
          mapping.type = property;
          mapping.value = processes[prop][property];
          var bpmnItem = find(processes[prop][property], function(x) {return x;});
          var bpmnId = bpmnItem.$.id;
          console.log("bpmnId: "+bpmnId);
            if(bpmnId!=undefined){
              var returnVal =  find(diagrams,function(x){
                if(x.bpmnElement===bpmnId){
                  console.log("element found: " + JSON.stringify(x,null,4));
                  return x;
                }
              });
              console.log("returned value: "+returnVal);
          }
          documents.push(mapping);
        }
      }
    }
     return documents;
  }
}



function find(items,f) {
    for(var key in items) { 
        var elem = items[key]; 
        if (f(elem)) { console.log(JSON.stringify(elem,null,4)); return elem;}
        if(typeof elem === "object") { 
            find(elem,f); // call recursively
        }
    }
}

Edit:

the console output is the following:

bpmnId: StartEvent_1
element found: {
    "id": "BPMNShape_1",
    "bpmnElement": "StartEvent_1"
}
returned value: undefined


bpmnId: SequenceFlow_9
element found: {
    "id": "BPMNEdge_SequenceFlow_10",
    "bpmnElement": "SequenceFlow_9",
    "sourceElement": "BPMNShape_1",
    "targetElement": "BPMNShape_Task_3"
}
returned value: undefined

etc, etc...

an exmaple of the input data

"BPMNDiagram": [
            {
                "$": {
                    "id": "BPMNDiagram_1",
                    "name": "procurement subprocess"
                },
                "BPMNPlane": [
                    {
                        "$": {
                            "id": "BPMNPlane_1",
                            "bpmnElement": "process"
                        },
                        "BPMNShape": [
                            {
                                "$": {
                                    "id": "BPMNShape_1",
                                    "bpmnElement": "StartEvent_1"
                                },
                                "Bounds": [
                                    {
                                        "$": {
                                            "height": "36.0",
                                            "width": "36.0",
                                            "x": "20.0",
                                            "y": "182.0"
                                        }
                                    }
                                ]
                            },
                            {
                                "$": {
                                    "id": "BPMNShape_Task_3",
                                    "bpmnElement": "Task_2"
                                },
                                "Bounds": [
                                    {
                                        "$": {
                                            "height": "50.0",
                                            "width": "110.0",
                                            "x": "100.0",
                                            "y": "175.0"
                                        }
                                    }
                                ]
                            },
                            {
                                "$": {
                                    "id": "BPMNShape_ExclusiveGateway_2",
                                    "bpmnElement": "ExclusiveGateway_2",
                                    "isMarkerVisible": "true"
                                },
                                "Bounds": [
                                    {
                                        "$": {
                                            "height": "50.0",
                                            "width": "50.0",
                                            "x": "250.0",
                                            "y": "175.0"
                                        }
                                    }
                                ]
                        }// it continues

Answer 1

Try with:

var mapToModel = function(res){
  var processes = res.definitions.process;
  var diagrams = res.definitions.BPMNDiagram; 
  var documents = [];
  for(var prop in processes) {
    if(processes.hasOwnProperty(prop)){
      var propertyNames = Object.getOwnPropertyNames(processes[prop]);
      for(var property in processes[prop]){
        var mapping ={};
        if(property==="$"){
          //do something with the process
        }else{
        //shapes
          mapping.hash = hash.hashCode(new Date().toString());
          mapping.type = property;
          mapping.value = processes[prop][property];
          var bpmnItem = find(processes[prop][property], function(x) {return x.$.id;});
          var bpmnId = bpmnItem.$.id;//value is ok

            if(bpmnId!=undefined){
              var returnVal;
              find(diagrams,function(x){

                if( x.$ != undefined && x.$.bpmnElement != undefined ){

                  if(x.$.bpmnElement===bpmnId){
                    {returnVal =  x;}
                  }
                }
              });

              console.log("return:"+ returnVal);
          }
          documents.push(mapping);
        }
      }
    }
     return documents;
  }
}

Answer 2

I don't exactly what you are going for, but undefined is not the same as null. In your code, you only return if f(elem) is truthy, so all other cases the result will be undefined (because you didn't return anything else). If if your code is failing with a more complex object, then it must not be finding anything.

EDIT: after looking at your example data, I don't see anywhere where an id fields matches bpmnElement, so your find function will never find anything.