How to call a web service from javascript

<script type="text/javascript" >
      function getResult()
      {
          var info = document.getElementById("InputText").value;
          HTML5.BusTracking.GetBySpot(info,SucceededCallback);
          alert(info);
      }
      function SucceededCallback(result)
      {
          alert("yes");
          document.getElementById("ResultText").html = result["Latitude"];
      }
      function FailedCallback()
      {
          alert(error.message());
      }
  </script>

[System.Web.Script.Services.ScriptService]
public class BusTracking : System.Web.Services.WebService
{

    [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public DataTable GetBySpot(string spot)
    {
        string conn = "Data Source=svhqdev01;Initial Catalog=Bustracking;Persist Security Info=True;User ID=bustrack;Password=abcd1234;MultipleActiveResultSets=True;Application Name=EntityFramework";
        DataTable table = new DataTable();
        table.TableName = "Result";

        using(SqlConnection connection=new SqlConnection(conn))
        {
            SqlCommand cmd = new SqlCommand("GetByspot",connection);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlParameter parameter = new SqlParameter("@spot", spot);
            cmd.Parameters.Add(parameter);
            connection.Open();
            SqlDataAdapter adapter=new SqlDataAdapter(cmd);
            SqlDataReader reader = cmd.ExecuteReader();
            table.Load(reader);
            return table;
        }
    }
}