Bootstrap4 表单

在本章中，我们将学习如何使用 Bootstrap 创建表单。Bootstrap 通过一些简单的 HTML 标签和扩展的类即可创建出不同样式的表单。

表单元素 <input> , <textarea> , 和 <select> elements 在使用 .form-control 类的情况下，宽度都是设置为 100%。

Bootstrap4 表单布局

  • 堆叠表单 (全屏宽度)：垂直方向
  • 内联表单：水平方向

Bootstrap 提供了两种类型的表单布局:

堆叠表单

以下实例使用两个输入框，一个复选框，一个提交按钮来创建堆叠表单：

实例

< form action = " " > < div class = " form-group " > < label for = " email " > Email address: </ label > < input type = " email " class = " form-control " placeholder = " Enter email " id = " email " > </ div > < div class = " form-group " > < label for = " pwd " > Password: </ label > < input type = " password " class = " form-control " placeholder = " Enter password " id = " pwd " > </ div > < div class = " form-group form-check " > < label class = " form-check-label " > < input class = " form-check-input " type = " checkbox " > Remember me </ label > </ div > < button type = " submit " class = " btn btn-primary " > Submit </ button > </ form >

尝试一下 »

显示效果：

内联表单

所有内联表单中的元素都是左对齐的。

注意：在屏幕宽度小于 576px 时为垂直堆叠，如果屏幕宽度大于等于576px时表单元素才会显示在同一个水平线上。

内联表单需要在 <form> 元素上添加 .form-inline 类。

以下实例使用两个输入框，一个复选框，一个提交按钮来创建内联表单：

实例

< form class = " form-inline " > < label for = " email " > Email address: </ label > < input type = " email " class = " form-control " id = " email " > < label for = " pwd " > Password: </ label > < input type = " password " class = " form-control " id = " pwd " > < div class = " form-check " > < label class = " form-check-label " > < input class = " form-check-input " type = " checkbox " > Remember me </ label > </ div > < button type = " submit " class = " btn btn-primary " > Submit </ button > </ form >

尝试一下 »

显示效果：

上面的实例元素排列看起来很紧凑，可以使用 .mr-sm-2 类来设置右边距，使用 .mb-2 类设置底部边距：

实例

< form class = " form-inline " action = " " > < label for = " email " class = " mr-sm-2 " > Email address: </ label > < input type = " email " class = " form-control mb-2 mr-sm-2 " placeholder = " Enter email " id = " email " > < label for = " pwd " class = " mr-sm-2 " > Password: </ label > < input type = " password " class = " form-control mb-2 mr-sm-2 " placeholder = " Enter password " id = " pwd " > < div class = " form-check mb-2 mr-sm-2 " > < label class = " form-check-label " > < input class = " form-check-input " type = " checkbox " > Remember me </ label > </ div > < button type = " submit " class = " btn btn-primary mb-2 " > Submit </ button > </ form >

尝试一下 »

显示效果：

表单行/网格

我们还可以使用 .col 类来控制表单元素的宽度和对齐方式，不需要使用间距类。 .col 类来控制的表单需要放在 .row 容器中。

以下实例将两个列并排显示：

实例

< form > < div class = " row " > < div class = " col " > < input type = " text " class = " form-control " id = " email " placeholder = " Enter email " name = " email " > </ div > < div class = " col " > < input type = " password " class = " form-control " placeholder = " Enter password " name = " pswd " > </ div > </ div > </ form >

尝试一下 »

显示效果：

如果网格要使用比较小的间距可以使用 .form-row 替代 .row:

实例

< form > < div class = " form-row " > < div class = " col " > < input type = " text " class = " form-control " id = " email " placeholder = " Enter email " name = " email " > </ div > < div class = " col " > < input type = " password " class = " form-control " placeholder = " Enter password " name = " pswd " > </ div > </ div > </ form >

尝试一下 »

表单验证

我们可以使用不同的验证类来设置表单的验证功能。

.was-validated 或 .needs-validation 添加到 <form> 元素中，input 输入字段将具有绿色（有效）或红色（无效）边框效果，用于说明表单是否需要输入内容。

.valid-feedback 或 .invalid-feedback 类用来告诉用户缺少什么信息，或者在提交表单之前需要完成什么。

实例

使用 .was-validated 类显示表单在提交之前需要填写的内容：

< form action = " " class = " was-validated " > < div class = " form-group " > < label for = " uname " > Username: </ label > < input type = " text " class = " form-control " id = " uname " placeholder = " Enter username " name = " uname " required > < div class = " valid-feedback " > 验证成功！ </ div > < div class = " invalid-feedback " > 请输入用户名！ </ div > </ div > < div class = " form-group " > < label for = " pwd " > Password: </ label > < input type = " password " class = " form-control " id = " pwd " placeholder = " Enter password " name = " pswd " required > < div class = " valid-feedback " > 验证成功！ </ div > < div class = " invalid-feedback " > 请输入密码！ </ div > </ div > < div class = " form-group form-check " > < label class = " form-check-label " > < input class = " form-check-input " type = " checkbox " name = " remember " required > 同意协议 < div class = " valid-feedback " > 验证成功！ </ div > < div class = " invalid-feedback " > 同意协议才能提交。 </ div > </ label > </ div > < button type = " submit " class = " btn btn-primary " > 提交 </ button > </ form >

尝试一下 »

实例

使用 .needs-validation，它将在表单提交之后验证缺少的内容。这里需要添加一些 JavaScript 代码才能使代码正常工作：

< form action = " " class = " needs-validation " novalidate > < div class = " form-group " > < label for = " uname " > Username: </ label > < input type = " text " class = " form-control " id = " uname " placeholder = " Enter username " name = " uname " required > < div class = " valid-feedback " > 验证成功！ </ div > < div class = " invalid-feedback " > 请输入用户名！ </ div > </ div > < div class = " form-group " > < label for = " pwd " > Password: </ label > < input type = " password " class = " form-control " id = " pwd " placeholder = " Enter password " name = " pswd " required > < div class = " valid-feedback " > 验证成功！ </ div > < div class = " invalid-feedback " > 请输入密码！ </ div > </ div > < div class = " form-group form-check " > < label class = " form-check-label " > < input class = " form-check-input " type = " checkbox " name = " remember " required > 同意协议 < div class = " valid-feedback " > 验证成功！ </ div > < div class = " invalid-feedback " > 同意协议才能提交。 </ div > </ label > </ div > < button type = " submit " class = " btn btn-primary " > 提交 </ button > </ form > < script > // 如果验证不通过禁止提交表单 (function() { 'use strict'; window.addEventListener('load', function() { // 获取表单验证样式 var forms = document.getElementsByClassName('needs-validation'); // 循环并禁止提交 var validation = Array.prototype.filter.call(forms, function(form) { form.addEventListener('submit', function(event) { if (form.checkValidity() === false) { event.preventDefault(); event.stopPropagation(); } form.classList.add('was-validated'); }, false); }); }, false); })(); </ script >

尝试一下 »