Amortization Schedule

function calcpmt(form){ if (form.principal.value.length==0){ alert("Please enter the principal amount."); return; } if (form.rate.value.length==0){ alert("Please enter the interest rate."); return; } if (form.term.value.length==0){ alert("Please enter the term in years."); return; } for (var j=0; j < form.principal.value.length; j++) { var ch=form.principal.value.substring(j,j+1); if ((ch < "0" || "9" < ch) && ch != ".") { alert("c="+ch); alert("The principal amount contains an invalid character ="+ch); return; } } for (var j=0; j < form.rate.value.length; j++) { var ch=form.rate.value.substring(j, j + 1); if ((ch < "0" || "9" < ch) && ch !=".") { alert("The interest rate contains an invalid character"); return; } } for (var j=0; j < form.term.value.length; j++) { var ch=form.term.value.substring(j,j + 1); if (ch < "0" || "9" < ch) { alert("The loan term contains an invalid character"); return; } } var i=(form.rate.value/12)/100; var prin=form.principal.value; var temp=Math.exp(Math.log(1+i)*(12*form.term.value)); var pmt=prin / ((1-(1/temp))/i); form.payment.value=pmt; roundoff(form); if (form.full.checked) { showschedule(form); } } function clearform(form) { form.payment.value=""; form.principal.value=""; form.term.value=""; form.rate.value=""; } function roundoff(form) { var r=""; for (var j=0;j < form.payment.value.length;j++){ if (form.payment.value.substring(j,j+1)=="."){ r = r+form.payment.value.substring(j,j+3); break; } r = r + form.payment.value.substring(j,j+1); } form.payment.value=r; } function roundit(amt){ var r = ""; var s = ""+amt; for (var j=0;j < s.length;j++){ if (s.substring(j,j+1)=="."){ r = r+s.substring(j,j+3); break; } r = r + s.substring(j,j+1); } return r; } function showschedule(form){ var balance=form.principal.value; var pmt=form.payment.value; var totint=0; var totprin=0; var interest = 0; var prin = 0; w=window.open("","schedule","scrollbars=yes,toolbar=yes,width=600,height=450"); w.document.open("text/html"); w.document.writeln(""); w.document.writeln(""); w.document.writeln("Amortization Schedule"); w.document.writeln(""); w.document.writeln("

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Amortization Schedule
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Loan Amount: "); w.document.writeln(form.principal.value); w.document.writeln(" Interest Rate: "+form.rate.value); w.document.writeln(" Loan Term (years): "+form.term.value); w.document.writeln(" Monthly Payment: "+form.payment.value); w.document.writeln("

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Year#"); w.document.writeln("	Total of Payments"); w.document.writeln("	Total Interest"); w.document.writeln("	Total Principal"); w.document.writeln("	Unpaid Balance"); for (var i=1;i<=form.term.value;i++){ w.document.write("
"+i+""); pmt = form.payment.value * 12; w.document.write("	"+roundit(pmt)+""); for (j=1;j<=12;j++){ interest = (balance*(form.rate.value/100)/12); totint += interest; prin = form.payment.value - interest; totprin += prin; balance -= prin; } w.document.write("	"+roundit(totint)); w.document.write("	"+roundit(totprin)); w.document.write("	"+roundit(balance)); totint = 0; totprin = 0; } w.document.writeln("

Note: Payments shown include principle and interest only

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"); w.document.writeln(""); w.document.writeln(""); w.document.close(); }