JavaScript - Entering the currency format depending upon currencies selected in dropdown box

In my project there is a textfield named as Amount
i need to enter the amount depending upon what i select the currencies in a drop down

If i select a currency name as "Ireland" then i can able to enter the amount
according to the country number format means
if i select "Riyal" and i enter the value in amount filed as "12345.934213" then
it should automatically assign "separators" but the decimal places should not be rounded

can anybody help me in this regard with a sample of code that suits with any type of locale/currencies in the word and which suits ISO Standards.