JS 验证表单不能为空（附源码）

实现代码

<!--index.wxml-->
<form class='form' bindsubmit='formSubmit' bindreset='formReset'>
  <input name='name' value='{{name}}' placeholder='请输入姓名'></input>
  <input name='phone' value='{{phone}}' placeholder='请输入电话'></input>
  <input name='gender' value='{{gender}}' placeholder='请输入性别'></input>
  <input name='age' value='{{age}}' placeholder='请输入年龄'></input>
  <button bindtap="sendMessage" type='primary' formType="submit">提交</button>
</form>
<