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FAQ Topic - Why does 1+1 equal 11? or How do I convert a string to a number? (2008-10-13)

P: n/a
-----------------------------------------------------------------------
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:

http://www.jibbering.com/faq/faq_not...e_convert.html

http://msdn2.microsoft.com/en-us/library/67defydd.aspx
--
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.

Oct 12 '08 #1
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2 Replies


P: n/a
On Oct 13, 7:00*am, "FAQ server" <javascr...@dotinternet.bewrote:
-----------------------------------------------------------------------
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:

http://www.jibbering.com/faq/faq_not...e_convert.html

http://msdn2.microsoft.com/en-us/library/67defydd.aspx

--
*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 athttp://jibbering.com/faq/index.html.
*The FAQ workers are a group of volunteers. *The sendings of these
*daily posts are proficiently hosted byhttp://www.pair.com.
just use parseInt:

alert(1 + parseInt('1'));

Oct 13 '08 #2

P: n/a
Fdream wrote:
On Oct 13, 7:00 am, "FAQ server" <javascr...@dotinternet.bewrote:
>-----------------------------------------------------------------------
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) `.
^^^^^^^^^^^^^^^^^^^^^
>[...]
just use parseInt:

alert(1 + parseInt('1'));
You should read texts more carefully (always a good strategy, but especially
on Usenet), and search the newsgroup's archives on how to use parseInt()
properly. (Incidentally, the text version of this FAQ entry should be
reformatted so that the important points are not overlooked that easily.)

And please trim your quotes to a reasonable minimum, as you can see here.
(That is also explained in FAQ 2.3.)
HTH

PointedEars
--
Prototype.js was written by people who don't know javascript for people
who don't know javascript. People who don't know javascript are not
the best source of advice on designing systems that use javascript.
-- Richard Cornford, cljs, <f8*******************@news.demon.co.uk>
Oct 13 '08 #3

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