array problem

hi there,
i got this 20 numbers to be printed in javascript.
the problem is we are not allowed to print out the number that already been read before.
please help, every single help would be appreciated :)

here you go


var aFirst = new Array(1,2,3,2,4,3,4,5,6,7,5,6,7,8,9,45,21,11,4,5);
var aSecond = new Array();

for(i=0; i<aFirst.length;i++)
{
if(checkSecond(i)) document.write(aFirst[i] + ", ")
}
function checkSecond(i)
{
for(y=0; y<aSecond.length; y++)
{
if(aFirst[i]==aSecond[y]) return 0;
}
aSecond[aSecond.length] = aFirst[i];
return 1;
}