Coffeescript memoization? - coffeescript

Question

I have a function that displays a number as a properly formatted price (in USD).
var showPrice = (function() {
var commaRe = /([^,$])(\d{3})\b/;
return function(price) {
var formatted = (price < 0 ? "-" : "") + "$" + Math.abs(Number(price)).toFixed(2);
while (commaRe.test(formatted)) {
formatted = formatted.replace(commaRe, "$1,$2");
}
return formatted;
}
})();
From what I've been told, repeatedly used regexes should be stored in a variable so they are compiled only once. Assuming that's still true, how should this code be rewritten in Coffeescript?

Answer 1

This is the equivalent in CoffeeScript
showPrice = do ->
commaRe = /([^,$])(\d{3})\b/
(price) ->
formatted = (if price < 0 then "-" else "") + "$" + Math.abs(Number price).toFixed(2)
while commaRe.test(formatted)
formatted = formatted.replace commaRe, "$1,$2"
formatted

Answer 2

You can translate your JavaScript code into CoffeeScript using js2coffee. For given code the result is:
showPrice = (->
commaRe = /([^,$])(\d{3})\b/
(price) ->
formatted = ((if price < 0 then "-" else "")) + "$" + Math.abs(Number(price)).toFixed(2)
formatted = formatted.replace(commaRe, "$1,$2") while commaRe.test(formatted)
formatted
)()
My own version is:
showPrice = do ->
commaRe = /([^,$])(\d{3})\b/
(price) ->
formatted = (if price < 0 then '-' else '') + '$' +
Math.abs(Number price).toFixed(2)
while commaRe.test formatted
formatted = formatted.replace commaRe, '$1,$2'
formatted
As for repeatedly used regexes, I don't know.