Format number with commas

format-commas.js

// Converts `1234567` => `"1,234,567"
// Does not support decimals yet
function formatNumberWithCommas (number) {
    return ('' + number)                      // Convert to a string
                .split('').reverse().join('') // Reverse the order of the characters (which are all digits at this point)
                .replace(/(...)/g, '$1,')     // Insert a comma after every three digits
                .split('').reverse().join('') // Un-reverse the characters
                .replace(/^,/, '');           // Remove any commas that were added to the beginning (i.e. if the number of digits was a multiple of three)
};