解决layui弹出层layer的area过大被遮挡的问题

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <title>Title</title>
 <link rel="stylesheet" href="layui/css/layui.css" rel="external nofollow" media="all">
</head>
<body>
<button id="dianji">点击</button>

<form class="layui-form" action="" id="id">
 <div class="layui-form-item">
  <label class="layui-form-label">单行输入框</label>
  <div class="layui-input-block">
   <input type="text" name="title" lay-verify="title" autocomplete="off" placeholder="请输入标题"
     class="layui-input">
  </div>
 </div>
 <div class="layui-form-item">
  <label class="layui-form-label">验证必填项</label>
  <div class="layui-input-block">
   <input type="text" name="username" lay-verify="required" lay-reqtext="用户名是必填项，岂能为空？" placeholder="请输入"
     autocomplete="off" class="layui-input">
  </div>
 </div>

 <div class="layui-form-item">
  <div class="layui-inline">
   <label class="layui-form-label">验证手机</label>
   <div class="layui-input-inline">
    <input type="tel" name="phone" lay-verify="required|phone" autocomplete="off" class="layui-input">
   </div>
  </div>
  <div class="layui-inline">
   <label class="layui-form-label">验证邮箱</label>
   <div class="layui-input-inline">
    <input type="text" name="email" lay-verify="email" autocomplete="off" class="layui-input">
   </div>
  </div>
 </div>
</form>

<script src="layui/layui.all.js"></script>
<script type="text/javascript">
 var layerIndex;
 var layerInitWidth;
 var layerInitHeight;
 var $;
 layui.use(['form', 'jquery'], function () {
  var form = layui.form;
  $ = layui.jquery;
  $("#dianji").click(function () {
   layer.open({
    type: 1,
    area: ['500px', '900px'],
    content: $('#id'), //这里content是一个DOM，注意：最好该元素要存放在body最外层，否则可能被其它的相对元素所影响
    btn: ['按钮一', '按钮二', '按钮三']
    , yes: function (index, layero) {
     //按钮【按钮一】的回调
    }
    , btn2: function (index, layero) {
     //按钮【按钮二】的回调

     //return false 开启该代码可禁止点击该按钮关闭
    }
    , btn3: function (index, layero) {
     //按钮【按钮三】的回调

     //return false 开启该代码可禁止点击该按钮关闭
    }
    , cancel: function () {
     //右上角关闭回调

     //return false 开启该代码可禁止点击该按钮关闭
    },
    success: function (layero, index) {
     //获取当前弹出窗口的索引及初始大小
     layerIndex = index;
     layerInitWidth = $("#layui-layer" + layerIndex).width();
     layerInitHeight = $("#layui-layer" + layerIndex).height();
     resizeLayer(layerIndex, layerInitWidth, layerInitHeight);
     form.render();
    }
   });

  })

 });

 function resizeLayer(layerIndex, layerInitWidth, layerInitHeight) {
  var windowWidth = $(document).width();
  var windowHeight = $(document).height();
  var minWidth = layerInitWidth > windowWidth ? windowWidth : layerInitWidth;
  var minHeight = layerInitHeight > windowHeight ? windowHeight : layerInitHeight;
  console.log("win:", windowWidth, windowHeight);
  console.log("lay:", layerInitWidth, layerInitHeight);
  console.log("min:", minWidth, minHeight);
  layer.style(layerIndex, {
   top: 0,
   width: minWidth,
   height: minHeight
  });
 }
</script>
</body>
</html>