How to perform search for element in an array in mongoose?

Question

My data has an array in which each object contains state and I need to filter from that value.

I have my data as follows,

"npi" : [ 
    {
        "npi" : "1013987536",
        "xm_score" : 70.3,
        "state" : "TX",
        "zip" : "78026",
        "lat" : 28.918592,
        "lon" : -98.54152,
        "specialty" : [ 
            "x065", 
            "x109"
        ]
    }, 
    {
        "npi" : "1023010527",
        "xm_score" : 70.0,
        "state" : "MA",
        "zip" : "02120",
        "lat" : 42.32918979,
        "lon" : -71.10625722,
        "specialty" : [ 
            "x065", 
            "x109"
        ]
    }, 
    {
        "npi" : "1033116371",
        "xm_score" : 70.9,
        "state" : "TN",
        "zip" : "37207",
        "lat" : 36.222188,
        "lon" : -86.773002,
        "specialty" : [ 
            "x067"
        ]
    }, 

    {
        "npi" : "1053435198",
        "xm_score" : 71.0,
        "state" : "KS",
        "zip" : "66160",
        "lat" : 39.05615308,
        "lon" : -94.61062748,
        "specialty" : [ 
            "x096", 
            "x067"
        ]
    }]

I need to searh for the states,

   var modelObj = {'npi': []};
  if (state) {
    modelObj.npi.state = state;
  } 

 match.find(modelObj).limit(10).exec(function(err,data) {
  callback(null, data);
  });

This is what i tried but this really didnt worked for me.an anyone please suggest me help.Thanks.