Add Comma Function in JavaScript is Too Greedy

Question

How can I modify the function below to make it stop adding commas once we hit the decimal marker?

addCommas = function(number) {
    if(number === undefined) {
        return '';
    }

    while(/(\d+)(\d{3})/.test(number.toString())) {
        number = number.toString().replace(/(\d+)(\d{3})/, '$1'+','+'$2');
    }

    return number;
}

addCommas(0.123456); // Outputs 0.123,456, should output 0.123456

If this isn't just an exercise for you to learn something, I'd probably use numeral.js: http://numeraljs.com/ — Paul, Nov 05 '14 at 19:00
possible duplicate of [How to print a number with commas as thousands separators in JavaScript](http://stackoverflow.com/q/2901102/1048572) — Bergi, Nov 05 '14 at 19:01

score 5 · Accepted Answer · answered Nov 05 '14 at 19:00

5

My method is to split the number into fractional and integer parts...

addCommas = function(number) 
{
    if (number === undefined)
        return '';
    var parts = number.toString().split(".");
    parts[0] = parts[0].replace(/\B(?=(\d{3})+(?!\d))/g, ",");
    return parts.join(".");
}

document.write( addCommas(0.123456) + "<br />" );
document.write( addCommas(123456.123456) + "<br />" );
document.write( addCommas(123456) + "<br />" );

answered Nov 05 '14 at 19:00

Lee Taylor

7,761
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1

+1 for doing what I was doing but in a much simpler and cleaner way. – Geeky Guy Nov 05 '14 at 19:01

score 4 · Answer 2 · answered Nov 05 '14 at 19:01

Just add ^[^.]* to the front of the pattern:

addCommas = function(number) {
    if(number === undefined) {
        return '';
    }

    while(/^[^.]*(\d+)(\d{3})/.test(number.toString())) {
        number = number.toString().replace(/(\d+)(\d{3})/, '$1'+','+'$2');
    }

    return number;
}

You only have to do that for the .test() call.

score 1 · Answer 3 · answered Nov 05 '14 at 19:00

I would break the string in two prior to using the regular expression. Such as:

RenanCommas = function(number) {
    if(number === undefined) {
        return '';
    }

    var parts = (number + "").split(".");
    var integerPart = parts[0];
    var decimalPart = parts.length > 1 ? parts[1] : "0";

    while(/(\d+)(\d{3})/.test(integerPart.toString())) {
        integerPart = integerPart.replace(/(\d+)(\d{3})/, '$1'+','+'$2');
    }

    return integerPart + "." + decimalPart;
}

Notice that you could also have decimalPart as an empty string. In that case, you could check whether or not it is empty before using it. If you use an empty string instead of "0", the last line would be something like:

    return integerPart + (decimalPart ? ("." + decimalPart) : "");

And when you run it:

RenanCommas(12121241243.1123131232); // outputs "12,121,241,243.112312"

anubhava · Answer 4 · 2014-11-05T19:26:35.990

1

This seems to be working:

addCommas = function(number) {
   return number.replace(/(\.\d+$)|(?!^)(?=(?:\d{3})+(?=\.|$))/g, function($0, $1) {
       return ($1)?$1:','; });
}

Examples:

addCommas('0.123456');
"0.123456"
addCommas('987654.123456');
"987,654.123456"
addCommas('987654321');
"987,654,321"

edited Nov 05 '14 at 19:26

answered Nov 05 '14 at 19:21

anubhava

761,203
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569
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Add Comma Function in JavaScript is Too Greedy

4 Answers4