JavaScript 表单验证

Question

我正在对必填字段使用 JavaScript 验证。这是我的 html

<form class="uk-form-stacked" name="myForm"  action="<?php echo base_url(); ?>admin/pages/create_service"  id="wizard_advanced_form" method="post" enctype="multipart/form-data" onsubmit="return myFunction(this)" novalidate>
                    <div data-uk-grid-margin="" class="uk-grid">
                    <div class="uk-width-medium-1-2">
                        <label for="service_title">Service Title<span class="req">*</span></label>
                        <input type="text"  name="service_title" id="validd"  class="md-input"  />
                        <p id="demo"></p>
                    </div>
                </div>
                    <div class="uk-grid">
                    <button type="submit" class="md-btn md-btn-primary md-btn-wave-light waves-effect waves-button waves-light" >Submit</button>
                </div>
            </form>

我的 JavaScript 是

    <script>
    function myFunction(form) {
   var x, text;
   x = document.getElementById("validd").value;
   if (x == null || x == "") {
    text = "Input not valid";

   }
     document.getElementById("demo").innerHTML = text;
     return false;

     }
     </script>

现在，当我的输入字段为空并且我提交表单时，它显示我的输入无效，这很好。但即使当我填写一些文本输入时，它也会显示未定义，而不是输入无效，而不是提交表单。请帮忙..

Answer 1

您忘记添加 else，如果条件不满足，它将返回 true。

 <script>
        function myFunction(form) {
       var x, text;
       x = document.getElementById("validd").value;
       if (x == null || x == "") {
        text = "Input not valid";
        document.getElementById("demo").innerHTML = text;
         return false;
       }
        else{
          return true;
       } 
         }
 </script>