Changing strings to numbers(easy...maybe)

**Kae Verens** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

MickG wrote:
[color=blue]
> Hi,
>
> Im trying to add 3 numbers together, instead of getting 1+2+3=6, I'm
> getting 123, how could I remedy this.[/color]

use parseInt(number ) to get a number

Kae

**Evertjan.** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

MickG wrote on 28 feb 2005 in comp.lang.javas cript:
[color=blue]
> Im trying to add 3 numbers together, instead of getting 1+2+3=6, I'm
> getting 123, how could I remedy this.
>[/color]

var a='1' // string !
var b='2' // string !
var c='3' // string !

r = a + b + c

alert(r) // returns string 123

r = +a + +b + +c

alert(r) // returns number 6

r = 1*a + 1*b + 1*c

alert(r) // returns number 6

--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

**Douglas Crockford** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

> I'm trying to add 3 numbers together, instead of getting 1+2+3=6, I'm[color=blue]
> getting 123, how could I remedy this.[/color]
[color=blue]
> a = document.fred.a aa.value; // extract the string of text typed into
> // the input box
> b = document.fred.b bb.value;
> c = document.fred.c cc.value;
> // the problem is on the next line, all the other lines are OK and
> // shouldn't be changed
> sum =a+b+c ;[/color]

sum = (+a) + (+b) + (+c);

See http://www.crockford.com/javascript/survey.html

If you leave out the parens, it could look like

sum = +a++b++c;

which would be very bad. It is better to be clear.

**Michael Winter** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

Kae Verens wrote:

To the OP: In future please read the FAQ before posting. See
<URL:http://jibbering.com/faq/>.

[snip]
[color=blue]
> use parseInt(number ) to get a number[/color]

parseInt(number , radix)

is almost always preferred.

There are faster ways to coerce a string to a number, namely unary plus:

+str1 + +str2

With the brief snippet shown by the OP, I'd suggest checking the
format of the user input before using it. Whilst parseInt will behave
somewhat sensibly when parsing a non-numeric string, it isn't very
useful to start adding NaNs.

function isInteger(s) {return /^(0|[1-9]\d*)$/.test(s);}

function sum(f) {
var e = f.elements,
a = e['a'],
b = e['b'],
c = e['c'];

if(!isInteger(a )) {
/* Instruct user that input A is invalid. */
return false;
}
if(!isInteger(b )) {
/* Instruct user that input B is invalid. */
return false;
}
if(!isInteger(c )) {
/* Instruct user that input C is invalid. */
return false;
}
e['total'].value = +a + +b + +c;
}

<form action="">
<input type="text" name="a">
<input type="text" name="b">
<input type="text" name="c">
<input type="text" name="total">
<input type="button" value="Sum" onclick="sum(th is.form);">
</form>

Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail.

**Randy Webb** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

Kae Verens wrote:
[color=blue]
> MickG wrote:
>
>[color=green]
>>Hi,
>>
>>Im trying to add 3 numbers together, instead of getting 1+2+3=6, I'm
>>getting 123, how could I remedy this.[/color]
>
>
> use parseInt(number ) to get a number[/color]

No. You use the unary + to get a number, depending on what you define as
a number.

parseInt('08') is a very prime example of the flaw of parseInt when not
used with a radix.

--
Randy
comp.lang.javas cript FAQ - http://jibbering.com/faq & newsgroup weekly

**mike** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

Or this !!

sum = (a-0) + (b-0) + (c-0);

**RobG** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

MickG wrote:[color=blue]
> Hi,
>
> Im trying to add 3 numbers together, instead of getting 1+2+3=6, I'm
> getting 123, how could I remedy this.
>[/color]

<URL:http://www.jibbering.c om/faq/#FAQ4_21>

--
Rob

**Randy Webb** · Jul 23 '05, 06:13 PM

Re: Changing strings to numbers(easy... maybe)

mike wrote:[color=blue]
> Or this !!
>
> sum = (a-0) + (b-0) + (c-0);
>[/color]

No, you should read this groups FAQ first.

Had you done that, you would have prevented at least two problems with
your post. I will leave it to you as an exercise to determine what those
problems are.

--
Randy
comp.lang.javas cript FAQ - http://jibbering.com/faq & newsgroup weekly

**Dr John Stockton** · Jul 23 '05, 06:14 PM

Re: Changing strings to numbers(easy... maybe)

JRS: In article <1a9c775a.05022 81145.4411e7c1@ posting.google. com>,
dated Mon, 28 Feb 2005 11:45:00, seen in news:comp.lang. javascript,
MickG <mickg77@hotmai l.com> posted :
[color=blue]
>Im trying to add 3 numbers together,[/color]

No, you are not. You are adding 3 strings (probably; at least one is a
string).
[color=blue]
> instead of getting 1+2+3=6, I'm
>getting 123, how could I remedy this.[/color]

By reading the newsgroup FAQ.

Michael : Matches to /^-\d+$/ are integers too.

Douglas :[color=blue]
> sum = (+a) + (+b) + (+c);
>If you leave out the parens, it could look like
> sum = +a++b++c;[/color]

When I leave them out, it looks like
sum = +a + +b + +c;

All:

"Numeric strings" commonly come from reading input controls.

In such cases it is often good to write

var Wotsit = + nameofWotsitcon trol.value
var Al = + nameofAlcontrol .value
var ...
// expression(s) using Wotsit /et al/

Firstly, the desired values are obtained in the desired form; after
that, they are used in expressions which are not cluttered by control
addressing. The gain on clarity will generally outweigh any minor loss
in performance.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://www.jibbering.c om/faq/> JL/RC: FAQ of news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> jscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.

**Michael Winter** · Jul 23 '05, 06:14 PM

Re: Changing strings to numbers(easy... maybe)

Dr John Stockton wrote:

[snip]
[color=blue]
> Michael : Matches to /^-\d+$/ are integers too.[/color]

Yes. It would be acceptable to prefix the number with a plus, too.

Perhaps I should have named the function, isPositiveDecim alInteger,
but that seems a little excessive. :)

[snip]

Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail.

**Dr John Stockton** · Jul 23 '05, 06:14 PM

Re: Changing strings to numbers(easy... maybe)

JRS: In article <1109635202.504 974.197080@f14g 2000cwb.googleg roups.com>
, dated Mon, 28 Feb 2005 16:00:02, seen in news:comp.lang. javascript,
mike <hillmw@charter .net> posted :[color=blue]
>Or this !!
>
>sum = (a-0) + (b-0) + (c-0);[/color]

Even sum = -(-a-b-c) is better than that (and is fairly short).

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://www.jibbering.c om/faq/> JL/RC: FAQ of news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> jscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.

Changing strings to numbers(easy...maybe)

Changing strings to numbers(easy...maybe)

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