javascript - 如何使用jquery防止清除表单中的表单字段无效？

Question

当表单提交时，如何防止清除表单字段，例如userid(如果它已经存在)。

我的代码

<form method="POST" role="form" class="form-horizontal">
                {% csrf_token %}
            <div class="form-group">
                <label class="col-sm-2 lab" for="id_username">Username *</label>
                <div class="col-sm-10">
                    <input  name="username" id='id_username' class='form-control' placeholder='Username' minlength="5" maxlength="15" type='text' required></div>
                </div>

            <div class="form-group">
                <label class="col-sm-2 lab" for="id_email">E-Mail *</label>
                <div class="col-sm-10" >
                    <input class='form-control' name="email" id='id_email' placeholder='user@mydomain.com' pattern="(^[a-zA-Z0-9_.+-]+@[a-zA-Z]+\.com$)|(^[a-zA-Z0-9_.+-]+@[a-zA-Z]+\.org$)|(^[a-zA-Z0-9_.+-]+@[a-zA-Z]+\.co\.in$)" maxlength="200" type='email' required>
                </div>
            </div>

            <div class="form-group">
                <label class="col-sm-2 lab">Password *</label>
                <div class="col-sm-10">
                    <input class="form-control" name="password1" id="id_password1" placeholder="Password" minlength="8" maxlength="15" type="password" required>
                </div>
            </div>
            <div class="form-group">
                <label class="col-sm-2 lab2">Password Confirmation *</label>
                <div class="col-sm-10">
                    <input class="form-control" name="password2" id="id_password2" placeholder="Confirm Password" minlength="8" maxlength="15" type="password" required>
                </div>
            </div>
       <input type="submit"/>
         </form>

这是我的代码，支持 django

Answer 1

如果表单无效，请尝试此操作，然后它会调用 preventDefault()

$(document).ready(function() {
  $('form').on('submit', function(e){
    // validation code here
    if(!valid) {
      e.preventDefault();
    }
  });
});