form 表单提交数据小记

<form id="formid"  name= "myform" method = 'post'  action = 'user_login_submit.action' onsubmit = "return checkUser();" >
其中checkUser返回false为不提交，你可以在checkUser中做数据校验

function checkUser(){
   var result = document.getElementById("userid").value;
   var password = document.getElementById("passid").value;
   if(result == ""  ){
     alert("用户名不能为空");
     return false;
   }
   if(password == ""  ){
    alert("密码不能为空");
     return false;
   }
  document.getElementById("formid").submit();  // 获取form的ID，然后调用它的submit方法
}

<form id="forms">
  <input name="name"/>
  <input name="age"/>
</form>
<script>
  let form = document.getElementById('forms')
  let data = new FormData(form)
  data.append('age', 12)
</script>

  <input type="file" name="pic" id="pic" accept="image/gif, image/jpeg" />

  <input type="file" accept="image/gif,image/jpeg,image/jpg,image/png,image/svg" ref="inputFile" :name="name" id="picture" @change="changePicture">

<input type="file" name="file" id="contactAttachments" class="attachment-file" accept="application/pdf">

let a = e.target.files || e.dataTransfer.files