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From: FAQ server on 28 Jan 2010 19:00
-----------------------------------------------------------------------
FAQ Topic - How do I format a Number as a String with
exactly 2 decimal places?
-----------------------------------------------------------------------

When formatting money for example, to format 6.57634 to
6.58, 6.5 to 6.50, and 6 to 6.00?

Rounding of x.xx5 is uncertain, as such numbers are not
represented exactly. See also:

http://jibbering.com/faq/#binaryNumbers

The statement ` n = Math.round(n * 100)/100 ` converts ` n ` to a ` Number ` value
close to a multiple of ` 0.01 `. However, there are some problems.
Converting the number to a string ` (n + "") `, does not give
trailing zeroes. Rounding numbers that are very close to ` x.5 `, for example,
` Math.round(0.49999999999999992) ` results ` 1 `.

ECMAScript Ed. 3.0 introduced ` Number.prototype.toFixed `.
There are bugs in JScript's implementation with certain numbers,
for example ` 0.07 `.

Function ` numberToFixed ` returns accurate results that are
consistent across implementations where ` n > 0 `.

var numberToFixed =
(function() {
return toFixedString;

function toFixedString(n, digits) {
var unsigned = toUnsignedString(Math.abs(n), digits);
return (n < 0 ? "-" : "") + unsigned;
}

function toUnsignedString(n, digits) {
var t, s = Math.round(n * Math.pow(10, digits)) + "",
start, end;
if (/\D/.test(s)) {
return "" + n;
}
s = padLeft(s, 1 + digits, "0");
start = s.substring(0, t = (s.length - digits));
end = s.substring(t);
if(end) {
end = "." + end;
}
return start + end; // avoid "0."
}
/**
* @param {string} input: input value converted to string.
* @param {number} size: desired length of output.
* @param {string} ch: single character to prefix to s.
*/
function padLeft(input, size, ch) {
var s = input + "";
while(s.length < size) {
s = ch + s;
}
return s;
}
})();

// Test results
document.writeln([
"numberToFixed(9e-3, 12) => " + numberToFixed(9e-3, 12),
"numberToFixed(1.255, 2) => " + numberToFixed(1.255, 2),
"numberToFixed(1.355, 2) => " + numberToFixed(1.355, 2),
"numberToFixed(0.1255, 3) => " + numberToFixed(0.1255, 3),
"numberToFixed(0.07, 2) => " + numberToFixed(0.07, 2),
"numberToFixed(0.0000000006, 1) => " + numberToFixed(0.0000000006, 1),
"numberToFixed(0.0000000006, 0) => " + numberToFixed(0.0000000006, 0)
].join("\n"));

http://www.merlyn.demon.co.uk/js-round.htm

http://msdn.microsoft.com/en-us/library/sstyff0z%28VS.85%29.aspx


The complete comp.lang.javascript FAQ is at
http://jibbering.com/faq/

--

The sendings of these daily posts are proficiently hosted
by http://www.pair.com.

From: Dr J R Stockton on 25 Feb 2010 16:55
In comp.lang.javascript message <4b62250a$0$272$14726298(a)news.sunsite.dk
>, Fri, 29 Jan 2010 00:00:03, FAQ server <javascript(a)dotinternet.be>
posted:
>FAQ Topic - How do I format a Number as a String with
>exactly 2 decimal places?

It is better not to use variables I J K L M N i j k l m n for things
which are not essentially of integer value. Likewise for identifiers of
more than one "arbitrary" character. There is little advantage in
applying the rule for "self-explanatory" identifiers, though it is often
easy enough to do so.

--
(c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05 IE 7.
Web <URL:http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
I find MiniTrue useful for viewing/searching/altering files, at a DOS prompt;
free, DOS/Win/UNIX, <URL:http://www.idiotsdelight.net/minitrue/> unsupported.
From: John G Harris on 26 Feb 2010 09:01
On Thu, 25 Feb 2010 at 21:55:00, in comp.lang.javascript, Dr J R
Stockton wrote:
>In comp.lang.javascript message <4b62250a$0$272$14726298(a)news.sunsite.dk
>>, Fri, 29 Jan 2010 00:00:03, FAQ server <javascript(a)dotinternet.be>
>posted:
>>FAQ Topic - How do I format a Number as a String with
>>exactly 2 decimal places?
>
>It is better not to use variables I J K L M N i j k l m n for things
>which are not essentially of integer value. Likewise for identifiers of
>more than one "arbitrary" character. There is little advantage in
>applying the rule for "self-explanatory" identifiers, though it is often
>easy enough to do so.

FORTRAN lives! :-(

John
--
John Harris
From: Dr J R Stockton on 27 Feb 2010 16:27
In comp.lang.javascript message <ZcvHg0CFR9hLFwtC(a)J.A830F0FF37FB96852AD0
8924D9443D28E23ED5CD>, Fri, 26 Feb 2010 14:01:41, John G Harris
<john(a)nospam.demon.co.uk> posted:
>On Thu, 25 Feb 2010 at 21:55:00, in comp.lang.javascript, Dr J R
>Stockton wrote:
>>In comp.lang.javascript message <4b62250a$0$272$14726298(a)news.sunsite.dk
>>>, Fri, 29 Jan 2010 00:00:03, FAQ server <javascript(a)dotinternet.be>
>>posted:
>>>FAQ Topic - How do I format a Number as a String with
>>>exactly 2 decimal places?
>>
>>It is better not to use variables I J K L M N i j k l m n for things
>>which are not essentially of integer value. Likewise for identifiers of
>>more than one "arbitrary" character. There is little advantage in
>>applying the rule for "self-explanatory" identifiers, though it is often
>>easy enough to do so.
>
>FORTRAN lives! :-(

It is permissible to copy useful conventions from elsewhere, even if
they are not mandatory here. But by exhibiting a knowledge of FORTRAN,
you may be taken as showing either your age or a nerdish character.

As it happens, I have before me, between keyboard and screen, an /echt/
FORTRAN card - its presence resulting from a recent discussion on the
merits of using a fixed-pitch font for code on Web pages, and my
contribution relating an initially hard-to-understand bug in a
colleague's HP FORTRAN program in the post-card era (an algorithmically
essential, but syntactically unnecessary, part of a statement was in
columns 73-80 of the screen).

--
(c) John Stockton, nr London, UK. ?@merlyn.demon.co.uk Turnpike v6.05.
Web <URL:http://www.merlyn.demon.co.uk/> - w. FAQish topics, links, acronyms
PAS EXE etc : <URL:http://www.merlyn.demon.co.uk/programs/> - see 00index.htm
Dates - miscdate.htm estrdate.htm js-dates.htm pas-time.htm critdate.htm etc.
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