FAQ Topic - How do I convert a Number into a String with exactly 2 decimal places? (2007-12-15)

[FAQ server]

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

 

[Dr J R Stockton]

In comp.lang.javascript message <[email protected].

function Stretch(Q, L, c) { var S = Q
if (c.length>0) while (S.length<L) { S = c+S }

^^^^^^^^^^^^^^^ That seems unnecessary in this context. Indeed, the
loop could be incorporated in StrU.

return S
}
function StrU(X, M, N) { // X>=0.0
var T, S=new String(Math.round(X*Number("1e"+N)))

^^^^^^^^^^^^^^ Math.pow is better

if (S.search && S.search(/\D/)!=-1) { return ''+X }

No need to .search; /\D/.test(St) is simpler
It would be better to left-pad that return value to width M+N+1

with (new String(Stretch(S, M+N, '0')))

^^^^ ISTR an expressed dislike of using with.
^^^ ^^^^^^ there should be no need for a new string.

return substring(0, T=(length-N)) + '.' + substring(T)
}

Number.prototype.toFixed= function(n){ return StrS(this,1,n)};

Tatty spacing.

 

[Bart Van der Donck]

Dr J R Stockton wrote:

[...]

Tatty spacing.

Maybe this is an occasion on how whitespace (and by extension) line-
end are handled in the daily FAQ-postings.

The nature of the application requires to start from
http://www.jibbering.com/faq/index.xml with all whitespaces and line-
ends as written in the source code.

This is not like browser displays where whitespace and EOL are treated
differently.

I had invented the following regular expressions in order to obtain a
(IMO) best possible Usenet-display:

"p" => "\n",
"/p" => "\n",
"em" => "_",
"/em" => "_",
"url" => "\n\n",
"/url" => "\n\n",
"ul" => "\n",
"/ul" => "\n",
"li" => "* ",
"/li" => "",
"moreinfo" => "\n\n",
"/moreinfo" => "\n\n",
"resource" => "\n\n",
"/resource" => "\n\n",
"icode" => "` ",
"/icode" => " `",
"code" => "\n\n",
"/code" => "\n\n",

Additional rules:
- If more than three successive end-of-lines characters occur, they
are replaced by two.
- Six trailing spaces are removed.
- End-of-lines at the beginning an end of every message are removed.

Sometimes this may lead to less-than-optimal results, but I'm afraid
there is no other possibility because the application needs some rules
anyway how it should display the input stream.

Quick link to the results:
http://groups.google.com/groups/search?q=author:[email protected]&scoring=d

For all clarity, this does not apply to the code line that you
mentioned as this is literally the same as the source.

 

[Bart Van der Donck]

Additional rules:
- If more than three successive end-of-lines characters occur, they
are replaced by two.
- Six trailing spaces are removed.

I meant leading spaces.