Passing Data to Callback functions?

[Numair Kaukab]

var unique_interests = window.facebook_interests.filter((v, i, a) => a.indexOf(v) === i);
       
       
       var input = map.getCenter();
       var a = input.lat();
       var b = input.lng();
       
       var latlng = {lat: a, lng: b};
       
       window.markersGP = [];
       
    
       
       for(var i=0; i<unique_interests.length; i++)
       {
       
       
       var request = {
    location: latlng,
    radius: '500',
    query: unique_interests[i]
  };
       
       
       console.log(request);
      
       service = new google.maps.places.PlacesService(map);
       service.textSearch(request, function (results, status){
           
           
           alert(request.query);
       
       
           
       });

Whenever the callback functions are called, the for loop has executed completely, and the alert() always print out the last value in the array. Is there any way to bind the data with the function call?