# Thread: Javascript Math to generate form value.

1. Registered User
Join Date
Jan 2010
Posts
1

## Javascript Math to generate form value.

ok so heres where I stand, I don't know too much about javascript. Just enough to get me by. I am a PHP developer, I know how to do this in PHP but the client insists on doing it through javascript.

Basically there are 3 different form values that determine the Premium Death Benefit Ratio.

This is the formula the client wants:
Premium to Death Benefit Ratio % (Created by formula = Annual (Level) Premium Amount (Divided by) Death Benefit Amount (equals a percentage) That percentage multiplied by Life Expectancy

The 3 form values in the formula would be Annual Premium Amount (fypremium), Death Benefit Amount (dbp), Life Expectancy (average_le)

I was messing around with javascript trying to figure it out and I have gotten no where since I am not used to writing formulas in JS. Anyways here is what I have so far:

Code:
```function calculateLE(inputFieldId1, inputFieldId2, inputFieldId3, outputFieldId){
var DBR;

var input = document.getElementById(inputFieldId).value;

DBA = document.getElementById(dbp).value;
LE  = document.getElementById(average_le).value;

formula = document.getElementById(fypremium).value / document.getElementById(dbp).value = formula3;
formula2 = document.getElementById(average_le).value * formula3;

if { APA = "" } {
document.getElementById(outputFieldId).value = "Error getting Annual Premium Amount";
}
else if { DBA = "" } {
document.getElementById(outputFieldId).value = "Error getting Death Benefit Amount";
}
else if { LE = "" } {
document.getElementById(outputFieldId).value = "Error getting Life Expectancy";
}
else {
document.getElementById(outputFieldId).value = formula3;
}
}```
Now I honestly have no clue if I am on the right track but what i've found on the net hasnt really pointed me in the right direction

Here is the form values.

Code:
```<input type="text" name="fypremium" id="fypremium" onblur="calculateLE('fypremium', 'dbp', 'average_le', 'premium_dbr')">
In a nut shell the values for the 3 inputs stated above will determine premium_dbr's value.

average_le * percentage = DBR (death benefit ratio);

If someone could point me in the right direction to finishing this id be very greatful.

2. Code:
```<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">

<script type="text/javascript">
var aObj=document.getElementsByTagName('fieldset')[0].getElementsByTagName('input');
var i=aObj.length;
while(i--) {
aObj[i].onfocus=function() {if(this.value==this.defaultValue){this.value='';}};
}
};

function calculateLE(inputField1, inputField2, inputField3, outputField){
var f = document.form1;
for(var i=0; i<arguments.length-1; i++) { // don't check DBR
var field = f[arguments[i]];
if(field.value==field.defaultValue) {
return; // field not filled
}
}

var APA = f[inputField1].value;
var DBA = f[inputField2].value;
var LE  = f[inputField3].value;

formula = APA / DBA;
f[outputField].value = (LE * formula).toFixed(2);
}
</script>

<style type="text/css">
form {width:15em;margin:auto;}
label {display:block;float:right;margin:3px 0;}
</style>

<body>
<form action="#" method="" name="form1">
<fieldset>
<label>dbp <input type="text" name="dbp" value="enter dbp"></label>
<label>average_le <input type="text" name="average_le" value="enter average_le"></label>
</fieldset>
<div>
</div>
</form>
</body>
</html>```