run user defined function, if number of user connected through sockets is atleast one - Nodejs

I am trying to find a way to stop setInterval(test,5000) function from running if no user is connected to the socket stop setInterval function as it causes lot of waste of resources.

I found the method but I dont know how to put it

io.engine.clientsCount  //this will tell number of users connected but only inside socket.on function.

below is my code:

var connectCounter = 0;  


app.get('/', function(req, res){
  res.sendFile(__dirname + '/index.html');
});


 function test()
  {
    httpk.get("api-url", function(res) {
        var body = ''; 
        res.on('data', function(data){
            body += data;
        });

        res.on('end', function() {
            var parsed = JSON.parse(body);
            console.log(parsed.johndoe.example1);
            nsp.emit('live-quote', parseFloat(parsed.johndoe.example1);
        });
    });
  }

     setInterval(test,5000);

nsp.on('connection', function(socket){


  //Make a http call
  connectCounter++;
  nsp.emit('live-users',connectCounter);
  console.log('1 user connected, Total Joined: '+connectCounter);

  socket.on('disconnect', function(){
    connectCounter--;
    nsp.emit('live-users',connectCounter);
    console.log('1 user disconnected, Total Left: '+connectCounter);


  });

console.log("total clients: "+io.engine.clientsCount);

if(io.engine.clientsCount >= 1)
{
  //do something
  //if I put setInterval here it will cause problems, that is for each connection it will run setInterval causing lot of http get request
  // meaning, if 100 users then 100 get request in 5 seconds (depending on setInterval time).
}

});

How do I best stop execution of SetInterval(test,5000) if no users connected?

via Murlidhar Fichadia