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From: FAQ server on 30 Jul 2010 19:00
-----------------------------------------------------------------------
FAQ Topic - Why does 1+1 equal 11? or How do I convert a
string to a number?
-----------------------------------------------------------------------

Variables are not typed; their values are. The conversion between a
string and a number happens automatically. Since plus (`+`) is
also used as in string concatenation, `'1' + 1` is equal to `'11'`.
The string determines what `+` does. To overcome this, first convert the
string to a number. For example: `+varname` or `Number(varname)` or
`parseInt(varname, 10)` or `parseFloat(varname)`.
Form control values are strings, as is the result from a `prompt`
dialog. Convert these to numbers before performing addition by using
the unary `+` operator: `+'1' + 1` result is `2`.

Additional Notes: <URL: http://jibbering.com/faq/notes/type-conversion/>
<URL: http://msdn.microsoft.com/en-us/library/67defydd%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 1 Aug 2010 16:31
In comp.lang.javascript message <4c53597c$0$285$14726298(a)news.sunsite.dk
>, Fri, 30 Jul 2010 23:00:02, FAQ server <javascript(a)dotinternet.be>
posted:

>FAQ Topic - Why does 1+1 equal 11? or How do I convert a
>string to a number?


>Form control values are strings,

That is true even for checkboxes, it seems.

In my IE & FF & Opera, checkbox.value is the string 'on'.

In my Safari and Chrome, it is 'on' if checked, else ''.

In all, I expect checkbox.checked is a boolean.

--
(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.
Command-prompt MiniTrue is useful for viewing/searching/altering files. Free,
DOS/Win/UNIX now 2.0.6; see <URL:http://www.merlyn.demon.co.uk/pc-links.htm>.
From: David Mark on 2 Aug 2010 03:36
On Aug 1, 4:31 pm, Dr J R Stockton <reply1...(a)merlyn.demon.co.uk>
wrote:
> In comp.lang.javascript message <4c53597c$0$285$14726...(a)news.sunsite.dk>, Fri, 30 Jul 2010 23:00:02, FAQ server <javascr...(a)dotinternet.be>
>
> posted:
>
> >FAQ Topic - Why does 1+1 equal 11? or How do I convert a
> >string to a number?
> >Form control values are strings,
>
> That is true even for checkboxes, it seems.

Why wouldn't it be?

>
> In my IE & FF & Opera, checkbox.value is the string 'on'.

Yes, that's the default value.

>
> In my Safari and Chrome, it is 'on' if checked, else ''.

That's a bit of a wacky implementation, but shouldn't cause any
trouble. Serialization functions skip checkboxes if they are
unchecked, so the reported value is irrelevant.

>
> In all, I expect checkbox.checked is a boolean.

It is.
From: Ry Nohryb on 2 Aug 2010 04:38
On Aug 1, 10:31 pm, Dr J R Stockton <reply1...(a)merlyn.demon.co.uk>
wrote:
> In comp.lang.javascript message <4c53597c$0$285$14726...(a)news.sunsite.dk>, Fri, 30 Jul 2010 23:00:02, FAQ server <javascr...(a)dotinternet.be>
>
> posted:
>
> >FAQ Topic - Why does 1+1 equal 11? or How do I convert a
> >string to a number?
> >Form control values are strings,
>
> That is true even for checkboxes, it seems.
>
> In my IE & FF & Opera, checkbox.value is the string 'on'.
>
> In my Safari and Chrome, it is 'on' if checked, else ''.
>
> In all, I expect checkbox.checked is a boolean.

All html elements' attributes are always strings, ISTM.
--
Jorge.
From: David Mark on 2 Aug 2010 04:49
On Aug 2, 4:38 am, Ry Nohryb <jo...(a)jorgechamorro.com> wrote:
> On Aug 1, 10:31 pm, Dr J R Stockton <reply1...(a)merlyn.demon.co.uk>
> wrote:
>
> > In comp.lang.javascript message <4c53597c$0$285$14726...(a)news.sunsite.dk>, Fri, 30 Jul 2010 23:00:02, FAQ server <javascr...(a)dotinternet.be>
>
> > posted:
>
> > >FAQ Topic - Why does 1+1 equal 11? or How do I convert a
> > >string to a number?
> > >Form control values are strings,
>
> > That is true even for checkboxes, it seems.
>
> > In my IE & FF & Opera, checkbox.value is the string 'on'.
>
> > In my Safari and Chrome, it is 'on' if checked, else ''.
>
> > In all, I expect checkbox.checked is a boolean.
>
> All html elements' attributes are always strings, ISTM.

But that's not an attribute (it's a DOM property). Why does it seem
the whole world is confused about this?

The only (direct) way to get an attribute value is with the
getAttribute method. It returns a string or null (the latter when the
attribute is not present). IE's implementation of this method in
versions prior to 8 (and Compatibility View in 8) is broken as
designed (it returns property values).

http://www.cinsoft.net/attributes.html
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