$ = function(id) { return document.getElementById(id); }

function isEmpty(str){
  return (str == null) || (str.length == 0);
}

function trim(str) {
  	return str.replace (/^\s+/, '').replace (/\s+$/, '');
}

function isNumeric(sText)
{
   var ValidChars = "0123456789.";
   var IsNumber=true;
   var Char;

 
   for (var i = 0; i < sText.length && IsNumber == true; i++) 
      { 
      Char = sText.charAt(i); 
      if (ValidChars.indexOf(Char) == -1) 
         {
         IsNumber = false;
         }
      }
   return IsNumber;
   
}