前端判空失效 script无法判空

<form method="post" class="layui-form" >
    <input name="username" id="doctorCode" placeholder="用户名"  type="text" lay-verify="required" class="layui-input" >
    <hr class="hr15">
    <input name="password" id="doctorPassword" lay-verify="required" placeholder="密码"  type="password" class="layui-input">
    <hr class="hr15">
    <input value="登录" lay-submit lay-filter="login" style="width:100%;" type="button" onclick="login()">
    <hr class="hr20" >
    <input value="注册" lay-submit lay-filter="login" style="width:100%;" type="submit">
    <hr class="hr20" >
    <a href="login-user.html"  class="layui-btn layui-btn-danger" style="width: 163px; height:40px;">用户登录</a>
    <a href="login-admin.html"  class="layui-btn layui-btn-danger" style="width: 162px; height:40px;">管理登录</a>
</form>