$(function (){
   $("#calculate_bmi").click(function(){
      var height = $("#bmi_height").val();
      var weight = $("#bmi_weight").val();
      
      var error = validateBmi(height, weight);
      
      if(error != ""){
         $("#bmiResultTable").slideUp("fast");
         alert(error);
         return false;
      }
      var bmi = Math.round(weight / Math.pow(height / 100,2), 1);

      $("#bmi_result").html(bmi);
      $("#bmiResultTable").slideDown("fast");
   });
});

function validateBmi(height, weight){
   var error = "";

   if(isNaN(height)){
      error += "Height must be a number\n";
   }
   if(height == ""){
      error += "Height must be a number\n";
   }
   if(isNaN(weight)){
      error += "Weight must be a number";
   }
   if(weight == ""){
      error += "Weight must be a number\n";
   }
   
   return error;
}