//*******************************************
//DO NOT REMOVE THIS COPYWRITE INFO!
//Bi-Weekly Vs. Monthly Loan Calculator
//2003 Daniel C. Peterson ALL RIGHTS RESERVED
//Created: 06/20/2003
//Last Modified: 06/20/2003
//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 #:5782-1237-101-1198
//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 formatNumberDec(num, places, comma) {

var isNeg=0;

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

    var myDecFact = 1;
    var myPlaces = 0;
    var myZeros = "";
    while(myPlaces < places) {
       myDecFact = myDecFact * 10;
       myPlaces = eval(myPlaces) + eval(1);
       myZeros = myZeros + "0";
    }
    
	onum=Math.round(num*myDecFact)/myDecFact;
		
	integer=Math.floor(onum);

	if (Math.ceil(onum) == integer) {
		decimal=myZeros;
	} else{
		decimal=Math.round((onum-integer)* myDecFact)
	}
	decimal=decimal.toString();
	if (decimal.length<places) {
        fillZeroes = places - decimal.length;
	   for (z=0;z<fillZeroes;z++) {
        decimal="0"+decimal;
        }
     }

   if(places > 0) {
      decimal = "." + decimal;
   }

   if(comma == 1) {
	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;
   } else {
      finNum=integer+""+decimal;
   }

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

	return finNum;
}


function computeForm(form) {

if(form.principal.value == "") {
   alert("Please enter the current principal balance owed.");
   form.principal.focus();
} else 
if(form.intRate.value == "") {
   alert("Please enter the annual interest rate percentage.");
   form.intRate.focus();
} else
if(form.months.value == "") {
   alert("Please enter the term of the loan in months.");
   form.months.focus();
} else {

  var prin1 = stripNum(form.principal.value);
  var prin2 = stripNum(form.principal.value);

  var i = stripNum(form.intRate.value);
  if (i >= 1.0) {
     i = i / 100.0;
  }
  var i1  = i / 12;
  var i2 = i / 26;

  var numPmts1 = stripNum(form.months.value);

  var pmt1 = computeMonthlyPayment(prin1, numPmts1, i);
  form.moPmt.value = "$" + formatNumberDec(pmt1,2,1);
  var pmt2 = pmt1 / 2;
  form.biwkPmt.value = "$" + formatNumberDec(pmt2,2,1);

  var count = 0;
  var prin = prin2;
  var intPort = 0;
  var prinPort = 0;
  var accumInt = 0;

  while(prin > 0) {

     if((prin + (prin * i)) > pmt2) {
        intPort = prin * i2;
        prinPort = pmt2 - intPort;
        prin = prin - prinPort;
        accumInt = accumInt + intPort;
     } else {
        intPort = prin * i2;
        prinPort = prin;
        prin = prin - prinPort;
        accumInt = accumInt + intPort;
     }

     count = count + 1;

  }

  var numPmts2 = count;

  var VmoInt = computeFixedInterestCost(prin1, i, pmt1);
  form.moInt.value = "$" + formatNumberDec(VmoInt,2,1);

  var VbiwkInt = accumInt;
  form.biwkInt.value = "$" + formatNumberDec(VbiwkInt,2,1);

  var VintSave = eval(VmoInt) - eval(VbiwkInt);
  form.intSave.value = "$" + formatNumberDec(VintSave,2,1);

    form.time.value = "In essence, what you are really doing is adding a 13th payment to your annual number of payments, and splitting it up between 26 bi-weekly payments. In your case means that by paying an extra $" + formatNumberDec(pmt1 / 26) + " every two weeks you will pay off your loan in " + parseInt(numPmts2 /26*12,10) + " months instead of the current " + numPmts1 + " months, and save $" + formatNumberDec(VintSave,2,1) + " in loan interest in the process.";

   }
		
}