Removing commas is potentially dangerous because, as others have mentioned in the comments, many locales use a comma to mean something different (like a decimal place).

I don't know where you got your string from, but in some places in the world "2,299.00" = 2.299

The Intl object could have been a nice way to tackle this problem, but somehow they managed to ship the spec with only a Intl.NumberFormat.format() API and no parse counterpart :(

The only way to parse a string with cultural numeric characters in it to a machine recognisable number in any i18n sane way is to use a library that leverages CLDR data to cover off all possible ways of formatting number strings http://cldr.unicode.org/

The two best JS options I've come across for this so far:

• https://github.com/google/closure-library/tree/master/closure/goog/i18n
• https://github.com/globalizejs/globalize

The toFixed() method returns a string but the toLocaleString() method expects a number so just convert your string to a number after using the toFixed() method with the parseFloat() function and then use the toLocaleString() method on it.

However, do note that you will have to manually append the leading 0 since the parseFloat() method removes any leading zeroes to the right of the decimal point.

Check this particular answer on another Stack Overflow thread that explains the reason why the parseFloat() method removes the leading zeroes after the decimal point.

var num = 66666.7
var parsedNum = (""+num).split('.')[1].length > 1 ?
    parseFloat(num.toFixed(2)).toLocaleString() : 
    parseFloat(num.toFixed(2)).toLocaleString() + '0';

console.log("original", num)
console.log("with comma", num.toLocaleString())
console.log("with 2 digit fixed", num.toFixed(2))
console.log("now working--", parsedNum)

If you're looking for a short and sweet solution:

const number = 12345678.99;

const numberString = String(number).replace(
    /^\d+/,
    number => [...number].map(
        (digit, index, digits) => (
            !index || (digits.length - index) % 3 ? '' : ','
        ) + digit
    ).join('')
);

// numberString: 12,345,678.99