Getting currency data out of an array
Work with indices instead of elseif statements

You should write a function that identifies the index of this.textContent in the currencyData array. Why not try something like this:

function myIndexOf(o) {    
    for (var i = 0; i &lt; currencyData.length; i++) {
        if (currencyData[i].currency == o) {
            return i;
        }
    }
    return -1;
}


Taken from this Stackoverflow answer.

Then you can run:

currentIndex = myIndexOf(this.textContent)
getCurrency(currencyData[currentIndex].currency, currencyData[currentIndex].symbol);


And it's entirely extensible.

Avoid unnecessary HTML updates

Seems like you can reduce $span to only update the innerHTML of a span element rather than reinitializing your span element each time you append it to $('.js-input-amount-prepend'). This would slightly shorten getCurrency