Problems with array from a while

I have two related tables "Friends" and "Messages" I make a query that throws all the ids of my friends and then send that result via ajax and make a evaluation with that result with an "if", in fact I have no problem, I throw the expected result, the problem is that I do not know how to make that result. I explain myself with coigo for better understanding

session_start();
include="conexion.php";

//esta es la consulta y el resultado es exitoso
 $query=mysqli_query($conexion,"SELECT * FROM
   amigos RIGHT JOIN
   mensajes ON amigos.para = mensajes.id_user ");
 while($row=mysqli_fetch_array($query)){ 

      echo json_encode(array("usuarios"=>$row["id_user"]));

 }
  //este es el resultado de mi consulta me esta arrojando justamente los ids que esperaba
    {"usuarios":26}, {"usuarios":6}, {"usuarios":8}, {"usuarios":19}

Well, let me explain, that result I send with the json_encode for back and in the js file when I recive that data what I would like to do the following:

//ejemplo en el success
success:function(data){
 console.log(data)//por la consola puedo ver el resultado
  //un ejemplo muy simple para que se pueda entender 
     if (data["usuarios"]==26 || data["usuarios"]==13){

       alert("numero de usuario no autoridado");
  }
}

As you can see the code is very simple and understandable I think, now I do not do anything with that code or show me an error or something, it is obvious that something is wrong or I'm not doing something right I would appreciate any help thanks