Round parseFloat number value to two deciml points

I have a function that does some math, and am using parseFloat.  The value it returns must be rounded to two decimal places.  I have tried Math.Round(value) but it returns nothing.  Is this because math.round does not work with parseFloat?  The script uses two fields, and is as follows:

function totalFields()
{
myTotal1 = document.myForm.before.value;
myTotal2 = document.myForm.after.value;
myBigTotal = [(parseFloat(myTotal1)-parseFloat(myTotal2))*100]/parseFloat(myTotal1);
return(myBigTotal)
}
function addemup()
{
document.myForm.grandtotal.value=totalFields();
}

How can I convert the value to something recognized by math.round(value), or is there another way of converting this to two decimal points?  A test value could be 12.55658334973432

Thanks in advance,

lance22
JavaScript Noob
lance22Asked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

GwynforWebCommented:
<script>
num='234.123453'
str=new String()
str=num
str=str.match(/^\d*\.\d{2}/)
alert(str)
</script>

GwynforWebCommented:
or

<script>
function convert(str){
str=str.match(/^\d*\.\d{2}/)
return str
}
</script>

<<form>
  <p><input type="text" name="t1">
<input type="button" value="convert" onclick="t1.value=convert(t1.value)"> </p>
</form>
GwynforWebCommented:
for your function do this

function totalFields()
{
myTotal1 = document.myForm.before.value;
myTotal2 = document.myForm.after.value;
myBigTotal = [(parseFloat(myTotal1)-parseFloat(myTotal2))*100]/parseFloat(myTotal1);

myBigTotal=myBigTotal+' '
myBigTotal=myBigTotal.match(/^\d*\.\d{2}/)
return(myBigTotal)
}
function addemup()
{
document.myForm.grandtotal.value=totalFields();
}
Determine the Perfect Price for Your IT Services

Do you wonder if your IT business is truly profitable or if you should raise your prices? Learn how to calculate your overhead burden with our free interactive tool and use it to determine the right price for your IT services. Download your free eBook now!

devicCommented:
hi lance22,

try this:
=======================
function totalFields()
{
      myTotal1 = document.myForm.before.value*1;
      myTotal2 = document.myForm.after.value*1;
      return Math.round(((myTotal1-myTotal2)*100)/myTotal1);
}
GwynforWebCommented:
oops that truncates

<script>
function convert(str){
str=str.match(/^\d*\.\d{3}/)*100
str=Math.round(str)/100
return str
}
</script>

<form>
  <p><input type="text" name="t1">
<input type="button" value="convert" onclick="t1.value=convert(t1.value)"> </p>
</form>

so your function is

function totalFields()
{
myTotal1 = document.myForm.before.value;
myTotal2 = document.myForm.after.value;
myBigTotal = [(parseFloat(myTotal1)-parseFloat(myTotal2))*100]/parseFloat(myTotal1);

myBigTotal=myBigTotal+' '
myBigTotal=myBigTotal.match(/^\d*\.\d{3}/)*100
myBigTotal=Math.round(myBigTotal)/100
return(myBigTotal)
}


Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
GwynforWebCommented:
After all that I think this is probably the most natural no ned for parseFloat, multiplying  a string variable returns a number so you can rearrange the expression to return the correct number

function totalFields()
{
myTotal1 = document.myForm.before.value;
myTotal2 = document.myForm.after.value;
myBigTotal = (myTotal1*100-myTotal2*100)/myTotal1;
myBigTotal=Math.round(100*myBigTotal)/100
return(myBigTotal)
}
JagataCommented:
Nice and simple, just use this in place of Math.round;

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

As per your example;

fltValue = 12.55658334973432
12.55658334973432 * 100 = 1255.658334973432
Math.round(1255.658334973432) = 1255
1255 / 100 = 12.55

So the function would output 12.55.
GwynforWebCommented:
Thats what I just said
JagataCommented:
I was just providing an OO solution. A concept sadly lost on many people.
GwynforWebCommented:
OO can not be implemeneted blindly without attention to the specifics of the problem. There are a number of type converison problems here
JagataCommented:
>> OO can not be implemeneted blindly without attention to the specifics of the problem.

I hardly think this is a blind implementation.

>> There are a number of type converison problems here

Including the error in your solution?
GwynforWebCommented:
What error?

ps

Math.round(1255.658334973432) = 1256  not 1255

so the output would be

1256 / 100 = 12.56
jaysolomonCommented:
Quite the flaming down please

You are hurting my ears
GwynforWebCommented:
I agree.  Just in case my proposed solution does not get lost in the above I suggest changing totalFields() to

function totalFields()
{
myTotal1 = document.myForm.before.value;
myTotal2 = document.myForm.after.value;
myBigTotal = (myTotal1*100-myTotal2*100)/myTotal1;
myBigTotal=Math.round(100*myBigTotal)/100
return(myBigTotal)
}
JagataCommented:
ps

Math.round(1255.658334973432) = 1256  not 1255

so the output would be

1256 / 100 = 12.56

-- Ah thanks dude, damn hope my code doesn't do that. :)
JagataCommented:
Heres another nice little example in the spirit of OO design;

            function roundFloat(fltValue, intDecimal) {
               return Math.round(fltValue * Math.pow(10, intDecimal)) / Math.pow(10, intDecimal)
            }

Not quite as simple as the other examples but this one lets you round to any number of decimal places. :) Just specify the number to be rounded (fltValue) and the number of decimal places (intDecimal).
ahosangFinance Systems DeveloperCommented:
lance22,
Not trying to clutter the thread, but after taking advice from the above comments which are needed for compatibility with older browsers, you can also make note of a built-in function that works on newer browsers:
var myNumber=1.222367;//example
alert(myNumber.toFixed(2));

the toFixed function is in Javascript 1.5
lance22Author Commented:
I appreciate everyone's help very much.  My wife had suggested .toFixed but this stuff will be used by people with OLD computers.  Thank you.
kajalgCommented:
the solution of regular expression doesn't work for decimal ranging between 0 and 1
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
JavaScript

From novice to tech pro — start learning today.