I need help with my script. I am trying to figure out the lowest maximum heart rate and highest maximum heart rate for exercise. New to javascript any help would be greatly appreciated.
here's what i have so far
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>HeartRate</title>
<script>
var age
max = function maxHeartRate(age)
{
(220-age);
}
</script>
</head>
<body>
<form>
<p>Age<input type="text" id="year" name="Year"></p>
<input type="button" value="Age Input" name="Age">
<onclick = maxHeartRate(age)>
</form>
<script>
var lowestTarget= max*.5
var maxTarget = max*.85
document.write("<p>" + "Max heart rate is " + max + "</p>");
document.write("<p>" + "Maximun Target rate is " + maxTarget + "</p>");
document.write("<p>" + "Lowest max rate is " + lowestTarget + "</p>");
</script>
</body>
</html>
hardware
prices 
