表单控件（Form control）
为<input>和<textarea>等文本表单控件提供自定义样式、大小、焦点状态等的升级。
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例子
<div class="mb-3">
<label for="exampleFormControlInput1" class="form-label">Email address</label>
<input type="email" class="form-control" id="exampleFormControlInput1" placeholder="name@example.com">
</div>
<div class="mb-3">
<label for="exampleFormControlTextarea1" class="form-label">Example textarea</label>
<textarea class="form-control" id="exampleFormControlTextarea1" rows="3"></textarea>
</div>大小
使用诸如.form-control-lg 和 .form-control-sm之类的类设置高度。
<input class="form-control form-control-lg" type="text" placeholder=".form-control-lg" aria-label=".form-control-lg example">
<input class="form-control" type="text" placeholder="Default input" aria-label="default input example">
<input class="form-control form-control-sm" type="text" placeholder=".form-control-sm" aria-label=".form-control-sm example">禁用
在输入上添加禁用的布尔属性disabled，使其显示为灰色，并删除指针事件。
<input class="form-control" type="text" placeholder="Disabled input" aria-label="Disabled input example" disabled>
<input class="form-control" type="text" placeholder="Disabled readonly input" aria-label="Disabled input example" disabled readonly>只读
在输入上添加readonly 属性以防止修改输入的值。只读输入看起来更轻（就像禁用的输入一样），但保留标准光标。
<input class="form-control" type="text" placeholder="Readonly input here..." aria-label="readonly input example" readonly>只读纯文本
如果要将表单中的<input readonly> 元素设置为纯文本样式，请使用.form-control-plaintext纯文本类删除默认表单字段样式并保留正确的边距和填充。
<div class="mb-3 row">
<label for="staticEmail" class="col-sm-2 col-form-label">Email</label>
<div class="col-sm-10">
<input type="text" readonly class="form-control-plaintext" id="staticEmail" value="email@example.com">
</div>
</div>
<div class="mb-3 row">
<label for="inputPassword" class="col-sm-2 col-form-label">Password</label>
<div class="col-sm-10">
<input type="password" class="form-control" id="inputPassword">
</div>
</div><form class="row g-3">
<div class="col-auto">
<label for="staticEmail2" class="visually-hidden">Email</label>
<input type="text" readonly class="form-control-plaintext" id="staticEmail2" value="email@example.com">
</div>
<div class="col-auto">
<label for="inputPassword2" class="visually-hidden">Password</label>
<input type="password" class="form-control" id="inputPassword2" placeholder="Password">
</div>
<div class="col-auto">
<button type="submit" class="btn btn-primary mb-3">Confirm identity</button>
</div>
</form>文件输入
<div class="mb-3">
<label for="formFile" class="form-label">Default file input example</label>
<input class="form-control" type="file" id="formFile">
</div>
<div class="mb-3">
<label for="formFileMultiple" class="form-label">Multiple files input example</label>
<input class="form-control" type="file" id="formFileMultiple" multiple>
</div>
<div class="mb-3">
<label for="formFileDisabled" class="form-label">Disabled file input example</label>
<input class="form-control" type="file" id="formFileDisabled" disabled>
</div>
<div class="mb-3">
<label for="formFileSm" class="form-label">Small file input example</label>
<input class="form-control form-control-sm" id="formFileSm" type="file">
</div>
<div>
<label for="formFileLg" class="form-label">Large file input example</label>
<input class="form-control form-control-lg" id="formFileLg" type="file">
</div>颜色
<label for="exampleColorInput" class="form-label">Color picker</label>
<input type="color" class="form-control form-control-color" id="exampleColorInput" value="#563d7c" title="Choose your color">数据表
数据列表允许您创建一组可从<input>中访问（并自动完成）的<option>。这些元素类似于<select>元素，但有更多的菜单样式限制和差异。虽然大多数浏览器和操作系统都支持<datalist> 元素，但它们的样式最多也不一致。
<label for="exampleDataList" class="form-label">Datalist example</label>
<input class="form-control" list="datalistOptions" id="exampleDataList" placeholder="Type to search...">
<datalist id="datalistOptions">
<option value="San Francisco">
<option value="New York">
<option value="Seattle">
<option value="Los Angeles">
<option value="Chicago">
</datalist>Sass
Variables
$input-* 在大多数表单控件（而不是按钮）中共享。
$input-padding-y: $input-btn-padding-y;
$input-padding-x: $input-btn-padding-x;
$input-font-family: $input-btn-font-family;
$input-font-size: $input-btn-font-size;
$input-font-weight: $font-weight-base;
$input-line-height: $input-btn-line-height;
$input-padding-y-sm: $input-btn-padding-y-sm;
$input-padding-x-sm: $input-btn-padding-x-sm;
$input-font-size-sm: $input-btn-font-size-sm;
$input-padding-y-lg: $input-btn-padding-y-lg;
$input-padding-x-lg: $input-btn-padding-x-lg;
$input-font-size-lg: $input-btn-font-size-lg;
$input-bg: $white;
$input-disabled-bg: $gray-200;
$input-disabled-border-color: null;
$input-color: $body-color;
$input-border-color: $gray-400;
$input-border-width: $input-btn-border-width;
$input-box-shadow: $box-shadow-inset;
$input-border-radius: $border-radius;
$input-border-radius-sm: $border-radius-sm;
$input-border-radius-lg: $border-radius-lg;
$input-focus-bg: $input-bg;
$input-focus-border-color: tint-color($component-active-bg, 50%);
$input-focus-color: $input-color;
$input-focus-width: $input-btn-focus-width;
$input-focus-box-shadow: $input-btn-focus-box-shadow;
$input-placeholder-color: $gray-600;
$input-plaintext-color: $body-color;
$input-height-border: $input-border-width * 2;
$input-height-inner: add($input-line-height * 1em, $input-padding-y * 2);
$input-height-inner-half: add($input-line-height * .5em, $input-padding-y);
$input-height-inner-quarter: add($input-line-height * .25em, $input-padding-y / 2);
$input-height: add($input-line-height * 1em, add($input-padding-y * 2, $input-height-border, false));
$input-height-sm: add($input-line-height * 1em, add($input-padding-y-sm * 2, $input-height-border, false));
$input-height-lg: add($input-line-height * 1em, add($input-padding-y-lg * 2, $input-height-border, false));
$input-transition: border-color .15s ease-in-out, box-shadow .15s ease-in-out;
$form-label-* 和 $form-text-* 用于 <label>和
.form-text 组件。
$form-label-margin-bottom: .5rem;
$form-label-font-size: null;
$form-label-font-style: null;
$form-label-font-weight: null;
$form-label-color: null;
$form-text-margin-top: .25rem;
$form-text-font-size: $small-font-size;
$form-text-font-style: null;
$form-text-font-weight: null;
$form-text-color: $text-muted;