表单验证（Validation）

通过浏览器默认行为或自定义样式和JavaScript，通过HTML5表单验证向用户提供有价值的、可操作的反馈。

On this page
虽然我们知道目前客户端的自定义验证样式和工具提示是无障碍的，自从它们不暴露于辅助技术。在处理解决方案时，我们仍建议使用服务器端选项或默认浏览器验证方法。

工作原理

下面是Bootstrap表单验证的工作原理：

  • HTML表单验证是通过CSS的两个伪类：invalid和：valid应用的。它适用于input、select和textarea元素。
  • Bootstrap 作用域：invalid和：valid样式到父.was-validated类，通常应用于form。否则，任何不带值的必填字段在页面加载时显示为无效。这样，您可以选择何时激活它们（通常在尝试提交表单之后）。
  • 要重置表单的外观（例如，在使用AJAX提交动态表单的情况下），请在提交后再次从form中移除.was-validated类。
  • As a fallback, .is-invalid and .is-valid 作为回退，.is-invalid and .is-valid类可以代替伪类用于服务器端验证。它们不需要.was-validated的父类。
  • 由于CSS工作方式的限制，如果没有自定义JavaScript的帮助，我们（目前）无法将样式应用到DOM中表单控件之前的label。
  • 所有现代浏览器都支持 约束验证API，这是一系列用于验证表单控件的JavaScript方法。
  • 反馈消息可以利用 浏览器默认值（每个浏览器的默认值不同，通过CSS不可改变）或我们的自定义反馈样式以及额外的HTML和CSS。
  • 您可以在JavaScript中使用setCustomValidity提供自定义有效性消息。

考虑到这一点，请考虑以下演示，以了解我们的自定义表单验证样式、可选服务器端类和浏览器默认值。

自定义样式

对于自定义Bootstrap表单验证消息，需要将novalidate布尔属性添加到form。这将禁用浏览器默认的反馈工具提示，但仍提供对JavaScript中表单验证api的访问。尝试提交以下表格；我们的JavaScript将截获提交按钮并向您传递反馈。尝试提交时，您将看到：invalid和：valid样式应用于表单控件。

自定义反馈样式应用自定义颜色、边框、焦点样式和背景图标来更好地传达反馈。select的背景图标仅适用于.form-select，而不适用于.form-control。

Looks good!
Looks good!
@
Please choose a username.
Please provide a valid city.
Please select a valid state.
Please provide a valid zip.
You must agree before submitting. 
<form class="row g-3 needs-validation" novalidate>
        <div class="col-md-4">
        <label for="validationCustom01" class="form-label">First name</label>
        <input type="text" class="form-control" id="validationCustom01" value="Mark" required>
        <div class="valid-feedback">
        Looks good!
        </div>
        </div>
        <div class="col-md-4">
        <label for="validationCustom02" class="form-label">Last name</label>
        <input type="text" class="form-control" id="validationCustom02" value="Otto" required>
        <div class="valid-feedback">
        Looks good!
        </div>
        </div>
        <div class="col-md-4">
        <label for="validationCustomUsername" class="form-label">Username</label>
        <div class="input-group has-validation">
        <span class="input-group-text" id="inputGroupPrepend">@</span>
        <input type="text" class="form-control" id="validationCustomUsername" aria-describedby="inputGroupPrepend" required>
        <div class="invalid-feedback">
          Please choose a username.
        </div>
        </div>
        </div>
        <div class="col-md-6">
        <label for="validationCustom03" class="form-label">City</label>
        <input type="text" class="form-control" id="validationCustom03" required>
        <div class="invalid-feedback">
        Please provide a valid city.
        </div>
        </div>
        <div class="col-md-3">
        <label for="validationCustom04" class="form-label">State</label>
        <select class="form-select" id="validationCustom04" required>
        <option selected disabled value="">Choose...</option>
        <option>...</option>
        </select>
        <div class="invalid-feedback">
        Please select a valid state.
        </div>
        </div>
        <div class="col-md-3">
        <label for="validationCustom05" class="form-label">Zip</label>
        <input type="text" class="form-control" id="validationCustom05" required>
        <div class="invalid-feedback">
        Please provide a valid zip.
        </div>
        </div>
        <div class="col-12">
        <div class="form-check">
        <input class="form-check-input" type="checkbox" value="" id="invalidCheck" required>
        <label class="form-check-label" for="invalidCheck">
          Agree to terms and conditions
        </label>
        <div class="invalid-feedback">
          You must agree before submitting.
        </div>
        </div>
        </div>
        <div class="col-12">
        <button class="btn btn-primary" type="submit">Submit form</button>
        </div>
        </form>
// Example starter JavaScript for disabling form submissions if there are invalid fields
        (function () {
        'use strict'
        
        // Fetch all the forms we want to apply custom Bootstrap validation styles to
          var forms = document.querySelectorAll('.needs-validation')
        
        // Loop over them and prevent submission
          Array.prototype.slice.call(forms)
        .forEach(function (form) {
        form.addEventListener('submit', function (event) {
          if (!form.checkValidity()) {
            event.preventDefault()
            event.stopPropagation()
          }
        
          form.classList.add('was-validated')
        }, false)
        })
        })()

浏览器的默认值

对自定义验证反馈消息或编写JavaScript来更改表单行为不感兴趣？很好，你可以使用浏览器的默认值。试着提交下面的表格。根据您的浏览器和操作系统，您将看到略有不同的反馈风格。

虽然这些反馈样式不能用CSS设置样式，但是您仍然可以通过JavaScript自定义反馈文本。

@ 
<form class="row g-3">
        <div class="col-md-4">
        <label for="validationDefault01" class="form-label">First name</label>
        <input type="text" class="form-control" id="validationDefault01" value="Mark" required>
        </div>
        <div class="col-md-4">
        <label for="validationDefault02" class="form-label">Last name</label>
        <input type="text" class="form-control" id="validationDefault02" value="Otto" required>
        </div>
        <div class="col-md-4">
        <label for="validationDefaultUsername" class="form-label">Username</label>
        <div class="input-group">
        <span class="input-group-text" id="inputGroupPrepend2">@</span>
        <input type="text" class="form-control" id="validationDefaultUsername"  aria-describedby="inputGroupPrepend2" required>
        </div>
        </div>
        <div class="col-md-6">
        <label for="validationDefault03" class="form-label">City</label>
        <input type="text" class="form-control" id="validationDefault03" required>
        </div>
        <div class="col-md-3">
        <label for="validationDefault04" class="form-label">State</label>
        <select class="form-select" id="validationDefault04" required>
        <option selected disabled value="">Choose...</option>
        <option>...</option>
        </select>
        </div>
        <div class="col-md-3">
        <label for="validationDefault05" class="form-label">Zip</label>
        <input type="text" class="form-control" id="validationDefault05" required>
        </div>
        <div class="col-12">
        <div class="form-check">
        <input class="form-check-input" type="checkbox" value="" id="invalidCheck2" required>
        <label class="form-check-label" for="invalidCheck2">
          Agree to terms and conditions
        </label>
        </div>
        </div>
        <div class="col-12">
        <button class="btn btn-primary" type="submit">Submit form</button>
        </div>
        </form>

服务器端验证

我们建议使用客户端验证，但如果需要服务器端验证，可以用.is-invalid和.is-valid指示无效和有效的表单字段。注意。这些类也支持无效反馈。

对于无效字段，请确保使用aria-describedby将无效反馈/错误消息与相关表单字段相关联（注意，如果该字段已指向其他表单文本，则此属性允许引用多个id）。

若要解决边界半径的问题，输入组需要额外的.has-validation。

Looks good!
Looks good!
@
Please choose a username.
Please provide a valid city.
Please select a valid state.
Please provide a valid zip.
You must agree before submitting. 
<form class="row g-3">
        <div class="col-md-4">
        <label for="validationServer01" class="form-label">First name</label>
        <input type="text" class="form-control is-valid" id="validationServer01" value="Mark" required>
        <div class="valid-feedback">
        Looks good!
        </div>
        </div>
        <div class="col-md-4">
        <label for="validationServer02" class="form-label">Last name</label>
        <input type="text" class="form-control is-valid" id="validationServer02" value="Otto" required>
        <div class="valid-feedback">
        Looks good!
        </div>
        </div>
        <div class="col-md-4">
        <label for="validationServerUsername" class="form-label">Username</label>
        <div class="input-group has-validation">
        <span class="input-group-text" id="inputGroupPrepend3">@</span>
        <input type="text" class="form-control is-invalid" id="validationServerUsername" aria-describedby="inputGroupPrepend3 validationServerUsernameFeedback" required>
        <div id="validationServerUsernameFeedback" class="invalid-feedback">
          Please choose a username.
        </div>
        </div>
        </div>
        <div class="col-md-6">
        <label for="validationServer03" class="form-label">City</label>
        <input type="text" class="form-control is-invalid" id="validationServer03" aria-describedby="validationServer03Feedback" required>
        <div id="validationServer03Feedback" class="invalid-feedback">
        Please provide a valid city.
        </div>
        </div>
        <div class="col-md-3">
        <label for="validationServer04" class="form-label">State</label>
        <select class="form-select is-invalid" id="validationServer04" aria-describedby="validationServer04Feedback" required>
        <option selected disabled value="">Choose...</option>
        <option>...</option>
        </select>
        <div id="validationServer04Feedback" class="invalid-feedback">
        Please select a valid state.
        </div>
        </div>
        <div class="col-md-3">
        <label for="validationServer05" class="form-label">Zip</label>
        <input type="text" class="form-control is-invalid" id="validationServer05" aria-describedby="validationServer05Feedback" required>
        <div id="validationServer05Feedback" class="invalid-feedback">
        Please provide a valid zip.
        </div>
        </div>
        <div class="col-12">
        <div class="form-check">
        <input class="form-check-input is-invalid" type="checkbox" value="" id="invalidCheck3" aria-describedby="invalidCheck3Feedback" required>
        <label class="form-check-label" for="invalidCheck3">
          Agree to terms and conditions
        </label>
        <div id="invalidCheck3Feedback" class="invalid-feedback">
          You must agree before submitting.
        </div>
        </div>
        </div>
        <div class="col-12">
        <button class="btn btn-primary" type="submit">Submit form</button>
        </div>
        </form>

支持的元素

验证样式可用于以下表单控件和组件：

  • <input>和带有.form-control的 <textarea>(在输入组中最多包括一个.form-control)
  • 带有.form-select的<select>
  • .form-checks
Please enter a message in the textarea.
Example invalid feedback text
More example invalid feedback text
Example invalid select feedback
Example invalid form file feedback
<form class="was-validated">
        <div class="mb-3">
        <label for="validationTextarea" class="form-label">Textarea</label>
        <textarea class="form-control is-invalid" id="validationTextarea" placeholder="Required example textarea" required></textarea>
        <div class="invalid-feedback">
        Please enter a message in the textarea.
        </div>
        </div>
        
        <div class="form-check mb-3">
        <input type="checkbox" class="form-check-input" id="validationFormCheck1" required>
        <label class="form-check-label" for="validationFormCheck1">Check this checkbox</label>
        <div class="invalid-feedback">Example invalid feedback text</div>
        </div>
        
        <div class="form-check">
        <input type="radio" class="form-check-input" id="validationFormCheck2" name="radio-stacked" required>
        <label class="form-check-label" for="validationFormCheck2">Toggle this radio</label>
        </div>
        <div class="form-check mb-3">
        <input type="radio" class="form-check-input" id="validationFormCheck3" name="radio-stacked" required>
        <label class="form-check-label" for="validationFormCheck3">Or toggle this other radio</label>
        <div class="invalid-feedback">More example invalid feedback text</div>
        </div>
        
        <div class="mb-3">
        <select class="form-select" required aria-label="select example">
        <option value="">Open this select menu</option>
        <option value="1">One</option>
        <option value="2">Two</option>
        <option value="3">Three</option>
        </select>
        <div class="invalid-feedback">Example invalid select feedback</div>
        </div>
        
        <div class="mb-3">
        <input type="file" class="form-control" aria-label="file example" required>
        <div class="invalid-feedback">Example invalid form file feedback</div>
        </div>
        
        <div class="mb-3">
        <button class="btn btn-primary" type="submit" disabled>Submit form</button>
        </div>
        </form>

工具提示

如果表单布局允许，可以将.{valid|invalid}-feedback类替换为.{valid|invalid}-tooltip类，以在样式化的工具提示中显示验证反馈。确保在工具提示定位时有一个带有position: relative的父级。在下面的示例中，我们的列类已经有了这种设置，但是您的项目可能需要另一种设置。

Looks good!
Looks good!
@
Please choose a unique and valid username.
Please provide a valid city.
Please select a valid state.
Please provide a valid zip. 
<form class="row g-3 needs-validation" novalidate>
        <div class="col-md-4 position-relative">
        <label for="validationTooltip01" class="form-label">First name</label>
        <input type="text" class="form-control" id="validationTooltip01" value="Mark" required>
        <div class="valid-tooltip">
        Looks good!
        </div>
        </div>
        <div class="col-md-4 position-relative">
        <label for="validationTooltip02" class="form-label">Last name</label>
        <input type="text" class="form-control" id="validationTooltip02" value="Otto" required>
        <div class="valid-tooltip">
        Looks good!
        </div>
        </div>
        <div class="col-md-4 position-relative">
        <label for="validationTooltipUsername" class="form-label">Username</label>
        <div class="input-group has-validation">
        <span class="input-group-text" id="validationTooltipUsernamePrepend">@</span>
        <input type="text" class="form-control" id="validationTooltipUsername" aria-describedby="validationTooltipUsernamePrepend" required>
        <div class="invalid-tooltip">
          Please choose a unique and valid username.
        </div>
        </div>
        </div>
        <div class="col-md-6 position-relative">
        <label for="validationTooltip03" class="form-label">City</label>
        <input type="text" class="form-control" id="validationTooltip03" required>
        <div class="invalid-tooltip">
        Please provide a valid city.
        </div>
        </div>
        <div class="col-md-3 position-relative">
        <label for="validationTooltip04" class="form-label">State</label>
        <select class="form-select" id="validationTooltip04" required>
        <option selected disabled value="">Choose...</option>
        <option>...</option>
        </select>
        <div class="invalid-tooltip">
        Please select a valid state.
        </div>
        </div>
        <div class="col-md-3 position-relative">
        <label for="validationTooltip05" class="form-label">Zip</label>
        <input type="text" class="form-control" id="validationTooltip05" required>
        <div class="invalid-tooltip">
        Please provide a valid zip.
        </div>
        </div>
        <div class="col-12">
        <button class="btn btn-primary" type="submit">Submit form</button>
        </div>
        </form>

Sass

Variables

$form-feedback-margin-top:          $form-text-margin-top;
        $form-feedback-font-size:           $form-text-font-size;
        $form-feedback-font-style:          $form-text-font-style;
        $form-feedback-valid-color:         $success;
        $form-feedback-invalid-color:       $danger;
        
        $form-feedback-icon-valid-color:    $form-feedback-valid-color;
        $form-feedback-icon-valid:          url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 8 8'><path fill='#{$form-feedback-icon-valid-color}' d='M2.3 6.73L.6 4.53c-.4-1.04.46-1.4 1.1-.8l1.1 1.4 3.4-3.8c.6-.63 1.6-.27 1.2.7l-4 4.6c-.43.5-.8.4-1.1.1z'/></svg>");
        $form-feedback-icon-invalid-color:  $form-feedback-invalid-color;
        $form-feedback-icon-invalid:        url("data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 12 12' width='12' height='12' fill='none' stroke='#{$form-feedback-icon-invalid-color}'><circle cx='6' cy='6' r='4.5'/><path stroke-linejoin='round' d='M5.8 3.6h.4L6 6.5z'/><circle cx='6' cy='8.2' r='.6' fill='#{$form-feedback-icon-invalid-color}' stroke='none'/></svg>");

Mixins

Two mixins are combined together, through our loop, to generate our form validation feedback styles.

@mixin form-validation-state-selector($state) {
        @if ($state == "valid" or $state == "invalid") {
        .was-validated #{if(&, "&", "")}:#{$state},
        #{if(&, "&", "")}.is-#{$state} {
        @content;
        }
        } @else {
        #{if(&, "&", "")}.is-#{$state} {
        @content;
        }
        }
        }
        
        @mixin form-validation-state(
        $state,
        $color,
        $icon,
        $tooltip-color: color-contrast($color),
        $tooltip-bg-color: rgba($color, $form-feedback-tooltip-opacity),
        $focus-box-shadow: 0 0 $input-btn-focus-blur $input-focus-width rgba($color, $input-btn-focus-color-opacity)
        ) {
        .#{$state}-feedback {
        display: none;
        width: 100%;
        margin-top: $form-feedback-margin-top;
        @include font-size($form-feedback-font-size);
        font-style: $form-feedback-font-style;
        color: $color;
        }
        
        .#{$state}-tooltip {
        position: absolute;
        top: 100%;
        z-index: 5;
        display: none;
        max-width: 100%; // Contain to parent when possible
            padding: $form-feedback-tooltip-padding-y $form-feedback-tooltip-padding-x;
        margin-top: .1rem;
        @include font-size($form-feedback-tooltip-font-size);
        line-height: $form-feedback-tooltip-line-height;
        color: $tooltip-color;
        background-color: $tooltip-bg-color;
        @include border-radius($form-feedback-tooltip-border-radius);
        }
        
        @include form-validation-state-selector($state) {
        ~ .#{$state}-feedback,
        ~ .#{$state}-tooltip {
        display: block;
        }
        }
        
        .form-control {
        @include form-validation-state-selector($state) {
        border-color: $color;
        
        @if $enable-validation-icons {
          padding-right: $input-height-inner;
          background-image: escape-svg($icon);
          background-repeat: no-repeat;
          background-position: right $input-height-inner-quarter center;
          background-size: $input-height-inner-half $input-height-inner-half;
        }
        
        &:focus {
          border-color: $color;
          box-shadow: $focus-box-shadow;
        }
        }
        }
        
        // stylelint-disable-next-line selector-no-qualifying-type
          textarea.form-control {
        @include form-validation-state-selector($state) {
        @if $enable-validation-icons {
          padding-right: $input-height-inner;
          background-position: top $input-height-inner-quarter right $input-height-inner-quarter;
        }
        }
        }
        
        .form-select {
        @include form-validation-state-selector($state) {
        border-color: $color;
        
        @if $enable-validation-icons {
          padding-right: $form-select-feedback-icon-padding-end;
          background-image: escape-svg($form-select-indicator), escape-svg($icon);
          background-position: $form-select-bg-position, $form-select-feedback-icon-position;
          background-size: $form-select-bg-size, $form-select-feedback-icon-size;
        }
        
        &:focus {
          border-color: $color;
          box-shadow: $focus-box-shadow;
        }
        }
        }
        
        .form-check-input {
        @include form-validation-state-selector($state) {
        border-color: $color;
        
        &:checked {
          background-color: $color;
        }
        
        &:focus {
          box-shadow: $focus-box-shadow;
        }
        
        ~ .form-check-label {
          color: $color;
        }
        }
        }
        .form-check-inline .form-check-input {
        ~ .#{$state}-feedback {
        margin-left: .5em;
        }
        }
        
        .input-group .form-control,
        .input-group .form-select {
        @include form-validation-state-selector($state) {
        z-index: 3;
        }
        }
        }

Map

This is the validation Sass map from _variables.scss. Override or extend this to generate different or additional states.

$form-validation-states: (
        "valid": (
        "color": $form-feedback-valid-color,
        "icon": $form-feedback-icon-valid
        ),
        "invalid": (
        "color": $form-feedback-invalid-color,
        "icon": $form-feedback-icon-invalid
        )
        );

Maps of $form-validation-states can contain three optional parameters to override tooltips and focus styles.

Loop

Used to iterate over $form-validation-states map values to generate our validation styles. Any modifications to the above Sass map will be reflected in your compiled CSS via this loop.

@each $state, $data in $form-validation-states {
        @include form-validation-state($state, $data...);
        }

Customizing

Validation states can be customized via Sass with the $form-validation-states map. Located in our _variables.scss file, this Sass map is how we generate the default valid/invalid validation states. Included is a nested map for customizing each state’s color, icon, tooltip color, and focus shadow. While no other states are supported by browsers, those using custom styles can easily add more complex form feedback.

Please note that we do not recommend customizing $form-validation-states values without also modifying the form-validation-state mixin.

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