Develop Reference

Display "$xx.90" instead of "$xx.9" in Javascript

When I use p=10000 ,r=15 and n=60 in the below ...
var x = parseFloat((Math.round(r/12/100*p/(1-Math.pow(1+ +(r/12/100),-n))*100)/100).toFixed(2));
x = 237.9 instead of 237.90.
If the combo of p, r and n result in a number that is not $xx.x", then the code snippet works fine ...ie. formats to 2 decimal places.
But why is it displaying 237.9 instead of 237.90?

When you call number.toFixed(2), you do indeed get a string representation of the number with two decimal digits:
var number = 237.9;
number.toFixed(2); // '237.90'
However, when you then use parseFloat on this, you convert it back to a number again; since a number does not contain information about the number of zeros to display, the last zero is dropped as it is printed:
parseFloat(number.toFixed(2)); // 237.9
To avoid this, simply don't convert your string back into a float, but use it as a string.

var x = parseFloat((Math.round(r/12/100*p/(1-Math.pow(1+ +(r/12/100),-n))*100)/100)).toFixed(2);
p=10000,r=15, n=60;
var x = parseFloat((Math.round(r/12/100*p/(1-Math.pow(1+ +(r/12/100),-n))*100)/100)).toFixed(2);
console.log(x)
Add toFixed after all operations. You need string, basically...

Converting Strings to Integer and get the persentage of two number

What I'm trying to do is to make a progress bar for donation. My html structure is:
<div class="hgoal" style="text-align: center;">My goal is to raise $<span id="mygoal">9,999.00</span></div>
<div class="donation-total">Total Donation<span id="total-donation">1,000.00</span></div>
my javascript so far is to get the innerHTML value of mygoal and total-donation.
var mygoal = document.getElementById("mygoal").innerHTML;
var totalgoal = document.getElementById("total-donation").innerHTML;
and I'm getting this as a result:
mygoal = "9,999.00";
total-donation = "1,000.00";
I believe this is a string and not an integer, and using parseInt() only give me the first digit number.
Can anyone give me an idea how can I make this into an integer that can use for computation? example:
mygoal + total-donation = 10,999.00
And also, any idea how can i get the percentage of this two varible?

Use .replace(/,/g,'') to replace commas, then you get the magic of type coercion to convert your string to a number during calculation...
var mygoal = document.getElementById("mygoal").innerHTML.replace(/,/g,'');
var totalgoal = document.getElementById("total-donation").innerHTML.replace(/,/g,'');
If you use + on strings, they will be appended to each other, but other mathematical operators (*/- etc...) will first coerce the strings into numbers. To force coercion, you can multiply by 1, or perhaps use Number("123123.123")...
Number(mygoal) + Number(totalgoal); // using addition, so coerce strings to numbers
(mygoal / total_donation) * 100; // does not need coercion

Your main issue is, that your numbers include colons. The parseFloat() call will work, once you replace these colons. You may use the following code to do so:
// define regexp to replace colons
var replaceColons = new RegExp(',', 'g');
// apply regex
num = num.replace(replaceColons, '');

mygoal=parseInt(mygoal.replace(/,/gi,"")) will give you mygoal=9999.

You should use parseFloat(), not parseInt() ...
More, you have to remove the commas from the string, since parseFloat() does not undertsand number formatting characters (like comma). So, for example:
mygoal = mygoal.replace(/,/g, '');
total_donation = total_donation.replace(/,/g, '');
To get the percentage of two numbers, use:
(mygoal / total_donation) * 100;
Note that in JavaScript you can't use 'minus' char (-) in variables names.
You could use for example 'underscore' char (_), or CamelCase, wich is the recommended style for variables in JavaScript.

You need to convert those Indian (maybe) numbers to valid Javascript numbers for the sum, then convert the output back to the initial format using Number.toLocaleString.
var mygoal = "9,999.00";
var total_donation = "1,000.00";
var total = Number((Number(mygoal.replace(/,/g, '')) + Number(total_donation.replace(/,/g, ''))).toFixed(2));
var finalResult = total.toLocaleString('en-IN',{minimumFractionDigits: 2 });
alert(finalResult);

How can I parse a string as an integer and keep decimal places if they are zeros?

I have these strings: "59.50" & "30.00"
What I need to do is convert them to integers but keep the trailing zeros at the end to effectively return:
59.50
30.00
I've tried:
Math.round(59.50 * 1000) / 1000
Math.round(30.00 * 1000) / 1000
but ended up with
59.5
30
I'm assuming I need to use a different method than Math.round as this automatically chops off trailing zeros.
I need to keep these as integers as they need to be multiplied with other integers and keep two decimals points. T thought this would be fairly straight forward but after a lot of searching I can't seem to find a solution to exactly what I need.
Thanks!

Your premise is flawed. If you parse a number, you are converting it to its numerical representation, which by definition doesn't have trailing zeros.
A further flaw is that you seem to think you can multiply two numbers together and keep the same number of decimal places as the original numbers. That barely makes sense.
It sounds like this might be an XY Problem, and what you really want to do is just have two decimal places in your result.
If so, you can use .toFixed() for this:
var num = parseFloat("59.50");
var num2 = parseFloat("12.33");
var num3 = num * num2
console.log(num3.toFixed(2)); // 733.64

Whenever you want to display the value of the variable, use Number.prototype.toFixed(). This function takes one argument: the number of decimal places to keep. It returns a string, so do it right before viewing the value to the user.
console.log((123.4567).toFixed(2)); // logs "123.46" (rounded)

To keep the decimals - multiply the string by 1
example : "33.01" * 1 // equals to 33.01

Seems you are trying to retain the same floating point, so better solution will be some thing like
parseFloat(string).toFixed(string.split('.')[1].length);

If you want numbers with decimal points, you are not talking about integers (which are whole numbers) but floating point numbers.
In Javascript all numbers are represented as floating point numbers.
You don't need the trailing zeros to do calculations. As long as you've got all the significant digits, you're fine.
If you want to output your result with a given number of decimal values, you can use the toFixed method to transform your number into a formatted string:
var num = 1.5
var output = num.toFixed(2) // '1.50'
// the number is rounded
num = 1.234
output = num.toFixed(2) // '1.23'
num = 1.567
output = num.toFixed(2) // '1.57'
Here's a more detailed description of toFixed: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toFixed

Plus operator problems in Jquery

I was trying with following script
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('#item1_number_1').keyup(function() {
var valone = $('#item1_number_1').val();
var valtwo = 5;
var total = ((valone) + (valtwo));
$('#item2_number_1').val(total.toFixed(2));
});
});
</script>
I do not get any result in the field. But when I assign multiple (*) instead of plus (+), I am getting result.
I cannot understand what the error is in "var total = ((valone) + (valtwo));"

You can only call toFixed on Numbers.
String * String will convert the strings to Numbers and multiply them giving you a Number.
String + String will concatenate the two Strings together giving you a String.
You need to convert the strings to Numbers manually before you try to add them together.
var total = (+valone) + (+valtwo);
Then Number + Number will add the two Numbers together giving you a Number.

The value of an input is always a string. "Adding" a string concatenates, giving another string. Strings do not have a toFixed method.
* however is unambiguously "multiply", giving a number and therefore a result.
var valone = parseFloat(document.getElementById('item1_number_1').value);

Use parseInt() to convert fetched value(valone ) to number, and calculate, something like this, please use this only when your number is not float(56.66),
var valone = parseInt($('#item1_number_1').val(), 10);
var valtwo = 5;
var total = ((valone) + (valtwo));
The fetched vaue is treated like string until you convert it into number.
UPDATE
After Archer pointed out, I came to know you are using toFixed() method, which supposed to expect float numbers. So in this case you should use parseFloat() as given below.
var valone = parseFloat($('#item1_number_1').val());

I think one of them is a string. Try parseInt(valone) to make it an int first.

The issue is the + operator can also be used to concat strings together. The * operator is ONLY for multiplication and therefore it implicitly converts your values to numbers.
So you either need to use parseInt, parseFloat, or Number to explicitly convert to a numeric type before using the + operator.

Javascript is treating variables as Strings, why?

I have the variable y, which is a subtotal. Its value is different depending on what happens with the html, but throughout the script I declared it like this:
var y = 21.78;
etc. Why is it that on my last equation where I add up the total, it treats them as strings when I want to add the values?
var tax = (0.055*y).toFixed(2);
var totalprice = y+tax;
/* totalprice holds "21.781.20" instead of 22.98 */

According to:
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Number/toFixed
toFixed() returns:
A string representation of number that does not use exponential
notation and has exactly digits digits after the decimal place.
thus, y+tax is cast to a string since one of the operands is a string.
In my opinion, this would make sense as Javascript's intrinsic numeric types do not have the ability to store a specific number of decimal place digits, so a string would be the most appropriate data structure to store this with.
I would advise you do all your addition before calling toFixed(), since the method is most suitable for formatting display output.
var taxRate = 0.055;
var subtotal = 21.78;
var tax = (taxRate * subtotal).toFixed(2),
totalprice = ((1+taxRate) * subtotal).toFixed(2);
document.write(totalprice);

The .toFixed() method returns a string. Try applying that method as the last step after all other calculations.

Here's a simple fix. Put '+' in front of the tax variable to convert it to a number.
var y = 21.78;
var tax = (0.055*y).toFixed(2);
var totalprice = y+ (+tax);
totalprice === 22.98;
If you don't want any rounding errors when you use toFixed, then include this re-implementation of it in your script.
http://bateru.com/news/2012/03/reimplementation-of-number-prototype-tofixed/

In my experience, if there's any chance available, Javascript will see the "+" sign as concatenate rather than addition. It's driven me nuts on more than one occasion. I will generally do this rather than chance concatenation:
var totalprice = parseInt(y)+parseInt(tax);

When letter replaces value, multiply with 1 when you're in need of +.
var totalprice = (y*1) + tax .
Other operands work fine, it's just the + operand that needs special treatment when variable replace value.