```html
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>BMI Caculate</title>
<h1>BIM calculator</h1>
</head>
<head>
<script>
var BMI={};
BMI.getBMI=function(a,b){
var bmi=b/((a/100)*(a/100));
return bmi;
};
BMI.idealweight=function(a){
var x=(a-100)*0.9;
x = x.toFixed(2);
return x;
};
function Cal(form){
var a=eval(form.height.value);
var b=eval(form.weight.value);
var bmi=eval(form.BMI.value);
var bmiValue =BMI.getBMI(a,b);
BMI.disp_alert(bmiValue );
form.BMI.value= bmiValue ;
}
BMI.disp_alert = function(bmi){
if (bmi < 18.5)
{
alert("You are underweight, please eat more!");
}
else if (bmi >= 18.5 && bmi < 25)
{
alert("Your weight is normal, please keep it up!");
}
else if (bmi >= 25 && bmi< 30)
{
alert("You are overweight, please lose weight!");
}
else
{
alert("Please lose weight!");
}
}
</script>
</head>
<body>
<form method=post>
Mass(kg):<input type="text" name="weight"><br>
<br/>
Height(cm):<input type="text" name="height"><br>
<br/>
<input type="button" value="Caculate BIM" onclick="Cal(this.form)">
<br/>
BMI=<input type="text" name="BMI">
</form>
</body>
</html>
```
num.toFixed(2)