//Controller
 public function user_ajukan_uji()
    {
     $user = DB::table('user')
                        ->select('id','nama_user','telp_user','email_user','kategori_user')
                        ->get();
     return Datatables::of($user)
            ->addColumn('Aksi', function($user) {
                return '<a onclick="('.$user->id.')" class="btn btn-md btn-primary" id="append"><i class="glyphicon glyphicon-arrow-down"></i>Pilih</a>';
            })
            ->make(true);
    }

//input box
<div class="col-md-2">
<input type="text" class="form-control" id="search" name="search" placeholder="Masukkan ID User">
</div>

//Script
<script>
function append(id){}
	$("#append").click (function(id){
    $("#search").append(".user->id.");
});
</script>