Question

check out my code

It works but jsfiddle hates it for some reason.
but when it’s ran in a browser i get NaN upon calculation

for some reason regardless of the parse it won’t return an integer to perform calculations on.

any one have an idea why?
also

// JavaScript Document
var payment

/* requirement #2* Each input (years, loan amount, interest rate)
   will have its own number pad for entry */
function getNum(id,span) {
    var a;
    a = parseInt(document.getElementById(id).value);
    document.getElementById(span).innerHTML += a;
}

function clear1(span) {
    document.getElementById(span).innerHTML = "";
}

/* requirment #7 Mortgage object with three variables:  years, amount, rate */
function Mortgage(years, amount, rate) {
    this.years = years;
    this.amount = amount;
    this.rate = rate;
    /*Requirment #8. Object must have an internal function that resets all
      values/variables to default and clears amounts displayed to user */
    this.clearAll = function() {
        document.getElementById(years).innerHTML = "";
        document.getElementById(amount).innerHTML = "";
        document.getElementById(rate).innerHTML = "";
    }
    /*gets the mortgage from spans*/                        
    this.getCalc = function() {
        /*Requirment # 9 Object must call at least 1 external function */
        get();
    }
}

function test() {          
    /*uses the params to call the spans id*/                     
    var c = new Mortgage('yInput','lInput','rInput');
    c.clearAll();
}

/* an external cunction to calculate mortgage*/
function get() {
    var m = new Mortgage(parseInt(document.getElementById('yInput').innerHTML),
                         parseInt(document.getElementById('lInput').innerHTML),
                         parseInt(document.getElementById('rInput').innerHTML)
    );

    /* this is NaN?*/
    document.write(m.years-m.rate);
}

function calculate() {
    var c = new Mortgage();
    c.getCalc();
}

http://jsfiddle.net/5qf7f/6/#run

Answer 1

In the part:

> /* this is NaN?*/
> document.write(m.years-m.rate);

Note that if the document has finished loading, a call to document.write will first call document.open, which clears the entire content of the document (including all scripts and the HTML element itself).

http://jsfiddle.net/5qf7f/6/#run

That “fiddle” doesn’t work at all for me. Better to reduce your code to an absolute minimum that displays the issue and post that. The exercise will likely lead you to your problem.

It might help your investigation to know that parseInt('') returns NaN.