var arr=[9, 7, 1, 9, 2, 3, 7, 4, 5, 4,7],
i,
arrayLength=arr.length,
out=[],
obj=[];

for (i=0; i < arrayLength; i++) {
   obj[arr[i]]=0;
}
  
for (i in obj) {
   out.push(i);
}
  
alert(out);

from this page: http://dreaminginjavascript.wordpress.com/2008/08/22/eliminating-duplicates/

Remove Duplicate Numbers in an Array

javascript

JavaScript