layui调用自定义方法提示未定义的解决办法

调用test()时提示未定义

layui.use(['layer', 'form', 'element'], function(){
  var layer = layui.layer
  ,form = layui.form
  ,element = layui.element
    function test(){
    //JS代码
    }
});

修改为

layui.use(['layer', 'form', 'element'], function(){
  var layer = layui.layer
  ,form = layui.form
  ,element = layui.element
   window.test = function(){
    //JS代码
    }
});