format_money.js

function formatCurrency(x, decimalPlaces, decimalSeparator, groupSeparator) {
    var parts = x.toString().split(".");
    parts[0] = parts[0].replace(/\B(?=(\d{3})+(?!\d))/g, groupSeparator);
    if(parts.length > 1) {
	parts[1] = parts[1].substring(0, decimalPlaces);	
    } else {
	parts[1] = '000000000'.substring(0, decimalPlaces);	
    }
    return parts.join(decimalSeparator);
}

function currency(amount, currencyCode) {
    var decimalSeparator = ",";
    var groupSeparator = " ";
    var decimalPlaces = 2;
    if(typeof(currencyCode) === 'undefined') {
	currencyCode = '';
    }
    /* US, GB, Thailand and a few other places uses different separator characters */
    if(currencyCode.match(/USD|GBP|THB/i) !== null) {
        decimalSeparator = ".";
        groupSeparator = ",";
    }
    var amountFormatted = formatCurrency(amount, decimalPlaces, decimalSeparator, groupSeparator);
    return amountFormatted + ' ' + currencyCode;
}

console.log('Amount: ' + currency(12345) );
console.log('Amount: ' + currency(12345, 'USD') );
console.log('Amount: ' + currency(12345.6789, 'EUR') );