// 
function fixElement(element, message){
	alert(message);
	element.focus();
	return;
}

function validate(form) {
	
	var passed=false;
	
	if (form.weight.value == "")
	{
	fixElement(form.weight, "Please enter your weight");
	}
	else if (isNaN(form.weight.value)){
	fixElement(form.weight, "Please enter a number in the weight field");
	}
	else if (form.height.value == "")
	{
	fixElement(form.height, "Please enter your height");
	}
	else if (isNaN(form.height.value)){
	fixElement(form.height, "Please enter a number in the weight field");
	}
		
	else {
		passed = true;
	}

	return passed;
}
	
function calculate(form){

validate(form);

	function decimate(n) {
  		var s = "" + Math.round(n * 100) / 100
  		var i = s.indexOf('.')
  		if (i < 0) return s + ".00"
  		var t = s.substring(0, i + 1) + s.substring(i + 1, i + 3)
  		if (i + 2 == s.length) t += "0"
  		return t
	}
	
	var weight = parseFloat(form.weight.value);
	var height = parseFloat(form.height.value);
	form.bmi.value = decimate((weight / (height*height))*703);
}

//