How to get count of documents available in MongoDb using NodeJs

I am trying to get number of documents available in my collection using NodeJS. I am getting number successfully in console but it is not sending response and showing below error:

RangeError [ERR_HTTP_INVALID_STATUS_CODE]: Invalid status code: 10 at ServerResponse.writeHead (_http_server.js:246:11) at ServerResponse._implicitHeader (_http_server.js:237:8) at ServerResponse.end (_http_outgoing.js:720:10) at ServerResponse.send (D:\Backend\aamku_con_backend\node_modules\express\lib\response.js:221:10) at D:\Backend\aamku_con_backend\routes\dealerCount.js:29:50 at executeCallback (D:\Backend\aamku_con_backend\node_modules\mongodb\lib\operations\execute_operation.js:74:5) at callbackWithRetry (D:\Backend\aamku_con_backend\node_modules\mongodb\lib\operations\execute_operation.js:122:14) at D:\Backend\aamku_con_backend\node_modules\mongodb\lib\operations\count_documents.js:36:7 at D:\Backend\aamku_con_backend\node_modules\mongodb\lib\operations\command_v2.js:90:9 at D:\Backend\aamku_con_backend\node_modules\mongodb\lib\cmap\connection_pool.js:308:13 { code: 'ERR_HTTP_INVALID_STATUS_CODE'

Below is my code:

router.get("/dealerCount", (req, res) => {        
  MongoClient.connect(dburl,{ useNewUrlParser: true, useUnifiedTopology: true },
    (err, client) => {
      if (err) {
        console.log("Error", err);
      } else {
        const coll = client.db("Mydb").collection("Dealers");

        coll.countDocuments(function(err, resp) {
          if (err) {
            console.log("Error", err);
          } else {
            console.log(resp);
            res.send(resp);
          }
        });
      }
    }
  );
});

How can I get total count in response?

The problem is res.send(resp); line. It is making express think that you are sending a integer which is not allowed. Replace that with this

res.send({"value": resp});

OR

res.send(resp.toString());