// Body Mass Index Calculator
// copyright 28th April 2006, by Stephen Chapman
// permission to use this Javascript on your web page is granted
// provided that all of the code in this script (including these
// comments) is used without any alteration
function valButton(btn) {
var cnt = -1;

for (var i=btn.length-1; i > -1; i--) 
{   
  if (btn[i].checked) {cnt = i; i = -1;}
}

if (cnt > -1) 
  return btn[cnt].value;
else return null;

}

function stripBlanks(fld) {
var result = "";
var c = 0;

for (i=0; i < fld.length; i++) 
{
if (fld.charAt(i) != " " || c > 0) 
  {result += fld.charAt(i);if (fld.charAt(i) != " ") c = result.length;}
}
return result.substr(0,c);
}

function calc(thisform) 
{
var d = valButton(thisform.d);
if (d == null) 
{
alert("You must choose centimetres/kg or inches/lb");
return false;
}

cv = d.split(',');;

var h = stripBlanks(thisform.h.value);

if (h == '') 
{
alert("You must enter your height");
thisform.h.focus();
return false;
}

if (h != Number(h) || (h = Number(h*cv[0]/100)) < 1 || h > 2.5) 
{
alert("Invalid height entered");
thisform.h.focus();
return false;
}

var w = stripBlanks(thisform.w.value);
if (w == '') 
{
alert("You must enter your weight");
thisform.w.focus();
return false;
}

if (w != Number(w) || (w = Number(w/cv[1])) < 25 || w > 250) 
{
alert("Invalid weight entered");
thisform.w.focus();
return false;
} 

thisform.f.value = Math.round(w / (h*h)*100)/100;}