FAQ Topic - How do I convert a Number into a String with exactly 2 decimal places?

Discussion in 'Javascript' started by FAQ server, Apr 14, 2007.

1. FAQ serverGuest

-----------------------------------------------------------------------
FAQ Topic - How do I convert a Number into 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 section 4.7 for Rounding issues.

N = Math.round(N*100)/100 only converts N to a Number of value
close to a multiple of 0.01; but document.write(N) does not give
trailing zeroes.

ECMAScript Ed. 3.0 (JScript 5.5 [but buggy] and JavaScript 1.5)
introduced N.toFixed, the main problem with this is the bugs in
JScripts implementation.

Most implementations fail with certain numbers, for example 0.07.
The following works successfully for M>0, N>0:

function Stretch(Q, L, c) { var S = Q
if (c.length>0) while (S.length<L) { S = c+S }
return S
}
function StrU(X, M, N) { // X>=0.0
var T, S=new String(Math.round(X*Number("1e"+N)))
if (S.search && S.search(/\D/)!=-1) { return ''+X }
with (new String(Stretch(S, M+N, '0')))
return substring(0, T=(length-N)) + '.' + substring(T)
}
function Sign(X) { return X<0 ? '-' : ''; }
function StrS(X, M, N) { return Sign(X)+StrU(Math.abs(X), M, N) }
Number.prototype.toFixed= function(n){ return StrS(this,1,n)};

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

http://msdn.microsoft.com/library/d...html/b5f03400-865e-4ab2-818c-f734c0f6d6f0.asp

===
Postings such as this are automatically sent once a day. Their
goal is to answer repeated questions, and to offer the content to
the community for continuous evaluation/improvement. The complete
comp.lang.javascript FAQ is at http://jibbering.com/faq/index.html.
The FAQ workers are a group of volunteers.

FAQ server, Apr 14, 2007

2. Dr J R StocktonGuest

In comp.lang.javascript message <46200b76\$0\$90270\$.
dk>, Fri, 13 Apr 2007 23:00:01, FAQ server <>
posted:

>FAQ Topic - How do I convert a Number into a String with
>exactly 2 decimal places?

>Most implementations fail with certain numbers, for example 0.07.
>The following works successfully for M>0, N>0:

but it is stale code.

> function Stretch(Q, L, c) { var S = Q
> if (c.length>0) while (S.length<L) { S = c+S }
> return S
> }
> function StrU(X, M, N) { // X>=0.0
> var T, S=new String(Math.round(X*Number("1e"+N)))
> if (S.search && S.search(/\D/)!=-1) { return ''+X }
> with (new String(Stretch(S, M+N, '0')))
> return substring(0, T=(length-N)) + '.' + substring(T)
> }
> function Sign(X) { return X<0 ? '-' : ''; }
> function StrS(X, M, N) { return Sign(X)+StrU(Math.abs(X), M, N) }
> Number.prototype.toFixed= function(n){ return StrS(this,1,n)};

StrS has its uses, but so do StrT and StrW.

It's a good idea to read the newsgroup c.l.j and its FAQ. See below.

--
(c) John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v6.05 IE 6
news:comp.lang.javascript FAQ <URL:http://www.jibbering.com/faq/index.html>.
<URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources.