Is there a functionality in JavaScript to convert values into specific locale formats?

Built-in, yes and no. There is Number.toLocaleString() but it is dependent on the system's locale.

However, there are some libraries which have modules for this. MooTools's Locale.Number for example allows you to convert a number into different locales (adding your own locale is trivial).

Locale.use("EU");
var inEuros = (50).formatCurrency(); // € 50,00

jsFiddle Demo

If you want the € sign to be printed after, you can simply create your own locale:

Locale.define('EU-suffix', 'Number', {
    currency: {
        suffix: ' €'
    }
}).inherit('EU', 'Number');