Parsing numbers with a comma decimal separator in JavaScript

Question

I used this function to check if a value is a number:

function isNumber(n) {
    return !isNaN(parseFloat(n)) && isFinite(n);
}

My program need to work with German values. We use a comma as the decimal separator instead of a dot, so this function doesn't work.

I tried to do this:

n.replace(",",".")

But it also doesn't seem to work. The exact function I tried to use is:

function isNumber(n) {
    n=n.replace(",",".");
    return !isNaN(parseFloat(n)) && isFinite(n);
}

The number looks like this 9.000,28 instead of the usual 9,000.28 if my statement wasn't clear enough.

Please post the full code using replace. That should be sufficient so there must be something else wrong. — James Montagne
– James Montagne, Commented Aug 23, 2013 at 14:24

rink.attendant.6 · Accepted Answer · 2013-08-23 14:36:30Z

37

You need to replace (remove) the dots first in the thousands separator, then take care of the decimal:

function isNumber(n) {
    'use strict';
    n = n.replace(/\./g, '').replace(',', '.');
    return !isNaN(parseFloat(n)) && isFinite(n);
}

edited Aug 23, 2013 at 14:36

answered Aug 23, 2013 at 14:28

rink.attendant.6

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4 Comments

Brigand Over a year ago

Fails with 111.222.3333,44. demo. .replace only replaces the first match unless you have a global regular expression. edit: whoops messed up the input string

rink.attendant.6 Over a year ago

@FakeRainBrigand Thanks, I updated my code.. not really good with regular expressions, does that seem right to you?

Brigand Over a year ago

Yeah, that's exactly right (I had it wrong in my original fiddle)

drew_w Over a year ago

This solution works for "nice" users but validation needs to work even for "bad" users. If you have the following (for example) this passes when it shouldn't: var testNumber = "10.0.0,000";

rink.attendant.6 · Accepted Answer · 2015-08-13 14:39:50Z

33

var number = parseFloat(obj.value.replace(",",""));

You'll probably also want this to go the other way...

obj.value = number.toLocaleString('en-US', {minimumFractionDigits: 2});

edited Aug 13, 2015 at 14:39

rink.attendant.6

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answered Dec 21, 2013 at 6:03

Anthony

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2 Comments

Dan Over a year ago

With this answer 123,4 gives you 1234 for the parse, and 1234.00 for the localisation. It's not answering the question, which is parsing comma decimal separators.

Des Over a year ago

Using toLocaleString is the best option for me, thank you.

Jonathan Batista · Accepted Answer · 2020-05-25 12:22:04Z

9

I believe the best way of doing this is simply using the toLocaleString method. For instance, I live in Brazil, here we have comma as decimal separator. Then I can do:

var number = 10.01;
console.log(number)
// log: 10.01

console.log(number.toLocaleString("pt-BR"));
// log: 10,01

answered May 25, 2020 at 12:22

Jonathan Batista

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