asked on

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

GwynforWeb

GwynforWeb

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>

GwynforWeb

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();
}

devic

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);
}

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GwynforWeb

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GwynforWeb

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)
}

Jagata

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.

GwynforWeb

Thats what I just said

Jagata

I was just providing an OO solution. A concept sadly lost on many people.

GwynforWeb

OO can not be implemeneted blindly without attention to the specifics of the problem. There are a number of type converison problems here

Jagata

>> 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?

GwynforWeb

What error?

ps

Math.round(1255.658334973432) = 1256 not 1255

so the output would be

1256 / 100 = 12.56

jaysolomon

Quite the flaming down please

You are hurting my ears

GwynforWeb

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)
}

Jagata

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. :)

Jagata

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).

ahosang

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

lance22

ASKER

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.

kajalg

the solution of regular expression doesn't work for decimal ranging between 0 and 1