var a = arr.sort(function (x, y ) {
       if (x>y) {return 1;
       } if (x<y) {return -1;
       } return 0;})
    var n = a[a.length-1];
    var L = [];
    var LL = [];
    var i;
    for (i=2; i<=n; i++) {L.push(i)}
    for (;;) {
       LL.push(L[0]);
       L = L.filter(function(x) {return x % L[0] != 0;});
       if (L.length <= 1) {
            LL.push(L[0]);
            break;}
}
    return arr.filter(function(x) {if (LL.indexOf(x) === -1) {return false;} else {return true;}});