How to remove extra decimal points?

Question

I need to alter users input and leave in the box only integer or decimal values, i.e. 4567 or 354.5635. I use the following statement:

v = v.replace(/[^\d\.]+/g, "");

But this allows multiple decimal points such as 345.45.345.67. How do I ensure that only one point is there?

If this is about the more general problem of checking if a string is numerical, regular expressions are not the best way - look here: http://stackoverflow.com/questions/18082/validate-numbers-in-javascript-isnumeric — wutz, Nov 15 '11 at 16:38
Why did you come to the conclusion that you need regular expressions here? — Lightness Races in Orbit, Nov 15 '11 at 16:40
So if the user inputs `"5.5.5"` or `"5.5abc"` what should happen? — Šime Vidas, Nov 15 '11 at 16:47
@Kizz: If it's so "obvious", how come it's wrong? :) What we need to take away from this is that your solution-selection protocol is broken. — Lightness Races in Orbit, Nov 15 '11 at 16:54
@Kizz I've created this question to solve your issue: http://stackoverflow.com/questions/8140612/remove-all-dots-except-the-first-one-from-a-string — Šime Vidas, Nov 15 '11 at 23:03
@ŠimeVidas: Your question is another prove of how important it is to phrase the title properly :) Thank you! — Kizz, Nov 16 '11 at 02:03

score 4 · Answer 1 · answered Nov 15 '11 at 17:03

4

v = parseFloat(v).toFixed(numberOfDecimalDigits);

answered Nov 15 '11 at 17:03

Ernest

570
3
6

parseFloat() is my favourite way, but be sure your float is small enough because parseFloat does not work well with high precision numbers like parseFloat('1.0000000000000001') – Mike Kovetsky Feb 11 '22 at 13:40

score 2 · Answer 2 · answered Nov 15 '11 at 17:35

Not sure if JS can do lookahead assertions, but if it can it could be done with a regex IF JS can also do reverse(input_string).

A reverse is needed because you want to allow the FIRST dot, and take out the rest.
However, search progresses left to right.

/(?:[.](?=.*[.])|[^\d.])+/g will take out all but the last '.'
So, the string has to be reversed, substituted, then reversed again.

Perl code example:

my $ss = 'asdf45.980.765';
$ss = reverse $ss;
$ss =~ s/(?:[.](?=.*[.])|[^\d.])+//g;
$ss = reverse $ss;
print $ss;

Output: 45.980765

This is the best solution ever. Works like a charm in my js script. — Vivek, Mar 25 '15 at 07:21

Shreya · Answer 3 · 2014-07-08T05:59:12.423

1

v = v.replace(/[A-Za-z$-]/g, ""); 
     // This will replace the alphabets

v = v.replace(/[^\d]*(\d+(\.\d+)?)?.*/g, "$1"); 
    // This will replace other then decimal

edited Jul 08 '14 at 05:59

answered Jul 08 '14 at 05:53

Shreya

21
4

These reg exps omits minus in negative values – Mike Kovetsky Feb 11 '22 at 13:42

yko · Accepted Answer · 2011-11-15T16:47:30.130

0

I'd recommend to use parseFloat here:

v = parseFloat(v);

This will guarantee you to have integer/decimal value or NaN.

edited Nov 15 '11 at 16:47

answered Nov 15 '11 at 16:38

yko

2,710
13
15

Thanks @TomalakGeret'kal I misunderstood question a bit – yko Nov 15 '11 at 16:42
No problem. :) [I could continue, by pointing out that decimal base is orthogonal from floating-point representation (and, if anything, "binary" would be appropriate), but I shan't...] – Lightness Races in Orbit Nov 15 '11 at 16:55
The project owner wants to replace all "wrong" input "on-the-fly" using txt's onblur and onkeyup handlers. I guess I either need to add some complicated logic to supplement that initial regex or I need to convince him to opt for a typical input validation and use parsing to test if the input is numeric. – Kizz Nov 15 '11 at 16:56
2

@Kizz, you better add input validation during the input, but instead of editing user input, highlight error. For example, make `$(input).css('background','red')` when something wrong entered. – yko Nov 15 '11 at 16:58

Eugene · Answer 5 · 2011-11-15T16:53:24.270

-1

v = v.replace(/[^\d]*(\d+(\.\d+)?)?.*/g, "$1");

edited Nov 15 '11 at 16:53

answered Nov 15 '11 at 16:31

Eugene

3,280
21
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This doesn't work. It even allows letters. The idea of my expression is not to allow anything except for digits and a dot. Hense the ^ char. Thanks though. – Kizz Nov 15 '11 at 16:37
Works for me: var v = ' 345.45.345.67'; v = v.replace(/[^\d]*(\d+(\.\d+)?).*/g, "$1"); console.log(v); // Outputs 345.45 – Eugene Nov 15 '11 at 16:43
@Eugene: That's hardly a rigorous test. A breaking test is really easy to come up with: feed `"a"` to your regular expression. – Lightness Races in Orbit Nov 15 '11 at 16:50
Let's say that the user inputs the letter "H". I need to disallow that, allowing only integers and an optional singledot. Your expression doesn't do that: txt.value = txt.value.replace(/[^\d]*(\d+(\.\d+)?).*/g, ""); If the txt.value is "H", it stays "H", nothing gets replaced. – Kizz Nov 15 '11 at 16:51
1

Choosing regular expressions for the task at hand is wrong, and this little trail of disasters is precisely why. – Lightness Races in Orbit Nov 15 '11 at 16:56
But how do you sanitize that input if it starts with a letter without regular expression? – Eugene Nov 15 '11 at 17:03
@Tomalak: I think you are right. I'd probably switch to normal input validation on submit. – Kizz Nov 15 '11 at 17:06
@Eugene: yko showed you half an hour ago: Javascript has had numeric parsing built-in for decades. – Lightness Races in Orbit Nov 15 '11 at 17:08
var v = 'a123.12'; v = parseFloat(v); console.log(v); // Output - NaN – Eugene Nov 15 '11 at 17:09
@Eugene: ... which is correct. Last I checked, `a123.12` is not a valid number. Do correct me if I'm wrong. – Lightness Races in Orbit Nov 15 '11 at 18:45
Quote - "I need to alter users input and leave in the box only integer or decimal values, i.e.". We are talking about sanitizing user's input. "built-in numeric parsing" won't do the job. – Eugene Nov 15 '11 at 21:43

How to remove extra decimal points?

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