localization - Does JavaScript take local decimal separators into account?

Question

I've got a web page that displays decimals in a user's localized format, like so:

• English: 7.75
• Dutch: 7,75

If I add two number variables together in JavaScript on my machine (where the numbers are taken from strings in the above formats) I get the following results:

• English: 7.75 + 7.75 = 15.5
• Dutch: 7,75 + 7,75 = 0

If I was to run this code on a Dutch users machine, should I expect the English-formatted addition to return 0, and the Dutch-formatted addition to return 15,5?

In short: Does the JavaScript calculation use local decimal separators in its string to number conversions?

Answer 1

Here's an example for a locale aware number parser:

function parseLocaleNumber(stringNumber, locale) {
    var thousandSeparator = Intl.NumberFormat(locale).format(11111).replace(/p{Number}/gu, '');
    var decimalSeparator = Intl.NumberFormat(locale).format(1.1).replace(/p{Number}/gu, '');

    return parseFloat(stringNumber
        .replace(new RegExp('\' + thousandSeparator, 'g'), '')
        .replace(new RegExp('\' + decimalSeparator), '.')
    );
}

It uses the passed locale (or the current locale of the browser if locale parameter is undefined) to replace thousand and decimal separators.

With a German locale setting

var n = parseLocaleNumber('1.000.045,22');

n will be equal to 1000045.22.

Update:

• Addressed Pointy's comment by using the regex class p{Number} for removing digits. So that it also works with non-arabic digits.
• Addressed Orion Adrian's comment to support languages where numbers are separated at every fourth digits.
• Added locale parameter to sepcify different locales for parsing.