JS确认删除

<script type="text/javascript">        
   window.onload = function () {
            document.getElementById('testID').onclick = test();
          function test() {
              if (confirm("你确认要删除吗?")) {
                  alert('删除成功');
              }
              else {
                  alert('删除失败');
              }
          }
        }
    </script>
    <input id="testID" type="button" value="删除">