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Thread: Javascript Math to generate form value.

  1. #1
    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;
    	
    	APA = document.getElementById(fypremium).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')">
    <input type="text" name="dbp" id="dbp" onblur="calculateLE('fypremium', 'dbp', 'average_le', 'premium_dbr')">
    <input type="text" name="average_le" id="average_le" 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.

    fypremium / dbp = percentage;
    average_le * percentage = DBR (death benefit ratio);

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

  2. #2
    Join Date
    Apr 2003
    Location
    Netherlands
    Posts
    21,654
    Code:
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
    <html lang="en">
    <head>
    <title></title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    
    <script type="text/javascript">
    window.onload=function() {
    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='';}};
        aObj[i].onblur=function() {if(this.value==''){this.value=this.defaultValue;}else{calculateLE('fypremium', 'dbp', 'average_le', 'premium_dbr')}};
        }
    };
    
    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) {
    			//alert(arguments[i]+' not filled');
    	        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">
    * {margin:0;padding:0;}
    form {width:15em;margin:auto;}
    label {display:block;float:right;margin:3px 0;}
    </style>
    
    </head>
    <body>
    <form action="#" method="" name="form1">
    <fieldset>
    <label>fypremium <input type="text" name="fypremium" value="enter fypremium"></label>
    <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>
    <label>premium_dbr <input type="text" name="premium_dbr" disabled></label>
    </div>
    </form>
    </body>
    </html>
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