所以我发现HTML5包含一个valid和invalid选择器。

input:required:focus {
  border: 1px solid red;
  outline: none;
  }

 textarea:required:focus {
 border: 1px solid red;
 outline: none;
 }

input:focus:valid {
border: 1px solid green;
outline: none;
}

input:focus:invalid {
border: 1px solid red;
outline: none;
}

input:valid {
border: 1px solid green;
}

您可以将它与required选择器结合使用来检查它是否有效，因此它是否填充，以及它是否正确，就像电话号码只包含数字一样。有趣的是，它只有HTML5和CSS3：）

你希望它什么时候变绿色？你开始输入的时候，还是当输入框失去焦点的时候？让我假设你希望它在失去焦点的时候变绿。另一个问题是：当它失去焦点时，它应该保持绿色吗？我假设它会，因为我的第一个假设是它只有在失去焦点时才会变绿。如果我的假设有错，请纠正我

Javascript：

$(function(){
        $('input:required,textarea:required').on('blur', function(){
           if($(this).val()!==''){  //assuming the form doesn't have some fields populated by default.
             $(this).addClass('green-border');
           } else {
             $(this).removeClass('green-border');
           }
        });
  });

.green-border {
  border: 1px solid green !important;  
}

input:required:focus {
  border: 1px solid red;
  outline: none;
}

textarea:required:focus {
  border: 1px solid red;
  outline: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet">
<form class="form-horizontal">

                <div class="form-group">
                    <label class="col-md-2 control-label" for="Name">Full name <span class="required">*</span></label>
                    <div class="col-md-10">
                        <input id="Name" name="Name" placeholder="Full name" class="form-control input-md" required="" type="text">
                        <span class="format-block"><a data-toggle="tooltip" data-placement="right" title="John Doe">Format</a></span>
                    </div>
                </div>

                <div class="form-group">
                    <label class="col-md-2 control-label" for="email">E-mail <span class="required">*</span></label>
                    <div class="col-md-10">
                        <input id="email" name="email" placeholder="E-mail" class="form-control input-md" required="" type="email">
                        <span class="format-block"><a data-toggle="tooltip" data-placement="right" title="johndoe@gmail.com">Format</a></span>
                    </div>
                </div>

                <div class="form-group">
                    <label class="col-md-2 control-label" for="phone">Phone number</label>
                    <div class="col-md-10">
                        <input id="phone" name="phone" placeholder="Phone number" class="form-control input-md" type="text">
                        <span class="format-block"><a data-toggle="tooltip" data-placement="right" title="Only numbers">Format</a></span>
                    </div>
                </div>

                <div class="form-group">
                    <label class="col-md-2 control-label" for="question">Question <span class="required">*</span></label>
                    <div class="col-md-10">
                        <textarea rows="20" cols="40" class="form-control" id="question" required="" name="question"></textarea>
                    </div>
                </div>

                <div class="col-md-10 col-md-offset-2">
                <button type="submit" class="btn btn-default formbuttonalign">Send mail!</button>
                </div>
        </form>

在必填字段上使用oninput事件，然后验证是否已填充。

oninput="if(this.value != ''){ this.style.borderColor='green'; } else{ this.style.borderColor='red'; }"

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