//*******************************************
//DO NOT REMOVE THIS COPYWRITE INFO!
//Auto Loan Vs. Home Equity Loan Calculator
//2002 Daniel C. Peterson ALL RIGHTS RESERVED
//Created: 10/31/2002
//Last Modified: 10/31/2002
//This script may not be copied, edited, distributed or reproduced
//without express written permission from
//Daniel C. Peterson of Web Winder Website Services
//For commercial use rates, contact:
//Dan Peterson:
//Web Winder Website Services
//P.O. Box 11
//Bemidji, MN  56619
//dan@webwinder.com
//http://www.webwinder.com
//Commercial User Licence #:5782-1237-77-1198
//Commercial Licence Date:2008-09-11
//*******************************************



function stripNum(num) {

   num=num.toString();


   var len = num.length;
   var rnum = "";
   var test = "";
   var j = 0;

   var b = num.substring(0,1);
   if(b == "-") {
      rnum = "-";
   }

   for(i = 0; i <= len; i++) {

      b = num.substring(i,i+1);

      if(b == "0" || b == "1" || b == "2" || b == "3" || b == "4" || b == "5" || b == "6" || b == "7" || b == "8" || b == "9" || b == ".") {
         rnum = rnum + "" + b;

      }

   }

   if(rnum == "" || rnum == "-") {
      rnum = 0;
   }

   rnum = Number(rnum);

   return rnum;

}



function computeMonthlyPayment(prin, numPmts, intRate) {

var pmtAmt = 0;

if(intRate == 0) {
   pmtAmt = prin / numPmts;
} else {
   
   if (intRate >= 1.0) {
     intRate = intRate / 100.0;
   }
   intRate /= 12;

   var pow = 1;
   for (var j = 0; j < numPmts; j++)
      pow = pow * (1 + intRate);

   pmtAmt = (prin * pow * intRate) / (pow - 1);

}

return pmtAmt;

}




function computeFixedInterestCost(principal, intRate, pmtAmt) { 

   var i = eval(intRate);
   if(i >= 1) {
   i /= 100;
   }
   i /= 12;

   var prin = eval(principal);
   var intPort = 0;
   var accumInt = 0;
   var prinPort = 0;
   var pmtCount = 0;
   var testForLast = 0;


   //CYCLES THROUGH EACH PAYMENT OF GIVEN DEBT
   while(prin > 0) {

      testForLast = (prin * (1 + i));

      if(pmtAmt < testForLast) {
         intPort = prin * i;
         accumInt = eval(accumInt) + eval(intPort);
         prinPort = eval(pmtAmt) - eval(intPort);
         prin = eval(prin) - eval(prinPort);
      } else {
      //DETERMINE FINAL PAYMENT AMOUNT
      intPort = prin * i;
      accumInt = eval(accumInt) + eval(intPort);
      prinPort = prin;
      prin = 0;
      }

      pmtCount = eval(pmtCount) + eval(1);

      if(pmtCount > 1000 || accumInt > 1000000000) {
         prin = 0;
      }

   }

return accumInt;

}




function formatNumber(num) {

var isNeg=0;

    if(num < 0) {
       num=num*-1;
       isNeg=1;
    }

    
	onum=Math.round(num*100)/100;
		
	integer=Math.floor(onum);

	if (Math.ceil(onum) == integer) {
		decimal="00";
	} else{
		decimal=Math.round((onum-integer)*100)
	}
	decimal=decimal.toString();
	if (decimal.length<2) decimal="0"+decimal;

	integer=integer.toString();
	var tmpnum="";
	var tmpinteger="";
	var y=0;

	for (x=integer.length;x>0;x--) {
		tmpnum=tmpnum+integer.charAt(x-1);
		y=y+1;
		if (y==3 & x>1) {
			tmpnum=tmpnum+",";
			y=0;
		}
	}

	for (x=tmpnum.length;x>0;x--) {
		tmpinteger=tmpinteger+tmpnum.charAt(x-1);
	}
		
	finNum=tmpinteger+"."+decimal;

    if(isNeg == 1) {
       finNum = "-" + finNum;
    }

	return finNum;
}


function computeForm(form) {
if(form.price.value.length == 0 || form.price.value == 0) {
   alert("Please enter the purchase price of the car.");
   form.price.focus();
} else
if(form.months.value.length == 0 || form.months.value == 0) {
   alert("Please enter the number of months you will be financing the car for.");
   form.months.focus();
} else
if(form.autoIntRate.value.length == 0) {
   alert("Please the auto loan's annual interest rate.");
   form.autoIntRate.focus();
} else
if(form.equityIntRate.value.length == 0) {
   alert("Please enter the home equity loan's annual interest rate.");
   form.equityIntRate.focus();
} else
if(form.saveRate.value.length == 0 || form.saveRate.value == 0) {
   alert("Please enter the annual interest rate you expect to earn from your savings.");
   form.saveRate.focus();
} else {

var Vprice = stripNum(form.price.value);
var VdownPay = stripNum(form.downPay.value);
var Vmonths = stripNum(form.months.value);
var VautoIntRate = stripNum(form.autoIntRate.value);
var VequityIntRate = stripNum(form.equityIntRate.value);
var VequityLoanCosts = stripNum(form.equityLoanCosts.value);
var VtaxRate = stripNum(form.taxRate.value);
var VsaveRate = stripNum(form.saveRate.value);

var VfinanceAmt = eval(Vprice) - (VdownPay);

var VautoPmt = computeMonthlyPayment(VfinanceAmt, Vmonths, VautoIntRate);
form.autoPmt.value = "$" + formatNumber(VautoPmt);

var VequityPmt = computeMonthlyPayment(VfinanceAmt, Vmonths, VequityIntRate);
form.equityPmt.value = "$" + formatNumber(VequityPmt);

//COMPUTE INTEREST COST
var VautoIntCost = computeFixedInterestCost(VfinanceAmt, VautoIntRate, VautoPmt);
form.autoIntCost.value = "$" + formatNumber(VautoIntCost);

var VequityIntCost = computeFixedInterestCost(VfinanceAmt, VequityIntRate, VequityPmt);
form.equityIntCost.value = "$" + formatNumber(VequityIntCost);

var VtaxSave = 0;
if(VtaxRate >= 1) {
   VtaxRate /= 100;
}

if(VautoIntCost > VequityIntCost) {

   VtaxSave = VequityIntCost * VtaxRate;
   form.equityTaxSave.value = "$" + formatNumber(VtaxSave);
   form.autoTaxSave.value = "N/A";

} else {

   form.equityTaxSave.value = "N/A";

}

   }
}