#format java
// LoanPayment JavaScript source

function calculate() {
    var principal = document.loandata.principal.value;
    var interest = document.loandata.interest.value / 100 / 12;
    var payments = document.loandata.years.value * 12;

    var x = Math.pow(1 + interest, payments);
    var monthly = (principal * x * interest) / (x-1);

    if(!isNaN(monthly) &&
            (monthly != Number.POSITIVE_INFINITY) &&
            (monthly != Number.NEGATIVE_INFINITY)) {
        document.loandata.payment.value = round(monthly);
        document.loandata.total.value = round(monthly * payments);
        document.loandata.totalinterest.value = round((monthly * payments) - principal);
    } else {
        document.loandata.payment.value = "";
        document.loandata.total.value = "";
        document.loandata.totalinterest.value = "";
    }
}

function round(x) {
    return Math.round(x*100)/100;
}