Possible to get javcascript to work in shortcode?

I have a basic javascript countdown timer and want to create a shortcode to display countdowns for different dates. The shortcode I created is:
There are [sc:countdown holiday="2015,12,25"] until Christmas!
…and then the shortcode contains the following but doesn’t work. The javascript works, just not in the shortcode:

<script>
var current="NO MORE DAYS"
var montharray=new Array("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec")

function countdown(yr,m,d){
var today=new Date()
var todayy=today.getYear()
if (todayy < 1000)
todayy+=1900
var todaym=today.getMonth()
var todayd=today.getDate()
var todaystring=montharray[todaym]+" "+todayd+", "+todayy
var futurestring=montharray[m-1]+" "+d+", "+yr
var difference=(Math.round((Date.parse(futurestring)-Date.parse(todaystring))/(24*60*60*1000))*1)
if (difference==0)
document.write(current)
else if (difference>0)
document.write(difference+" days")
}
//enter the count down date using the format year/month/day
countdown(2015,9,14)
</script>
<script type="text/javascript"> countdown(%%holiday%%)</script>

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