我想创建一个多选下拉列表。实际上，我必须使用下拉菜单选择多个选项。当我简单地这样做时，如下所示：
<select>
<option><input type="checkbox"></option>
</select>
然后复选框显示在下拉字段的前面。但我想为每个选项而不是整体创建它，以便我可以选择多个选项。有没有办法做到这一点？
【问题讨论】：
标签： javascript html css
这是一个简单的下拉清单：
var checkList = document.getElementById('list1');
checkList.getElementsByClassName('anchor')[0].onclick = function(evt) {
if (checkList.classList.contains('visible'))
checkList.classList.remove('visible');
else
checkList.classList.add('visible');
}.dropdown-check-list {
display: inline-block;
}
.dropdown-check-list .anchor {
position: relative;
cursor: pointer;
display: inline-block;
padding: 5px 50px 5px 10px;
border: 1px solid #ccc;
}
.dropdown-check-list .anchor:after {
position: absolute;
content: "";
border-left: 2px solid black;
border-top: 2px solid black;
padding: 5px;
right: 10px;
top: 20%;
-moz-transform: rotate(-135deg);
-ms-transform: rotate(-135deg);
-o-transform: rotate(-135deg);
-webkit-transform: rotate(-135deg);
transform: rotate(-135deg);
}
.dropdown-check-list .anchor:active:after {
right: 8px;
top: 21%;
}
.dropdown-check-list ul.items {
padding: 2px;
display: none;
margin: 0;
border: 1px solid #ccc;
border-top: none;
}
.dropdown-check-list ul.items li {
list-style: none;
}
.dropdown-check-list.visible .anchor {
color: #0094ff;
}
.dropdown-check-list.visible .items {
display: block;
}<div id="list1" class="dropdown-check-list" tabindex="100">
<span class="anchor">Select Fruits</span>
<ul class="items">
<li><input type="checkbox" />Apple </li>
<li><input type="checkbox" />Orange</li>
<li><input type="checkbox" />Grapes </li>
<li><input type="checkbox" />Berry </li>
<li><input type="checkbox" />Mango </li>
<li><input type="checkbox" />Banana </li>
<li><input type="checkbox" />Tomato</li>
</ul>
</div>【讨论】：
这不能仅在 HTML 中完成（将表单元素放入 option 元素中）。
或者您可以只使用标准的select multiple 字段。
<select multiple>
<option value="a">a</option>
<option value="b">b</option>
<option value="c">c</option>
</select>
【讨论】：
var expanded = false;
function showCheckboxes() {
var checkboxes = document.getElementById("checkboxes");
if (!expanded) {
checkboxes.style.display = "block";
expanded = true;
} else {
checkboxes.style.display = "none";
expanded = false;
}
}.multiselect {
width: 200px;
}
.selectBox {
position: relative;
}
.selectBox select {
width: 100%;
font-weight: bold;
}
.overSelect {
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
}
#checkboxes {
display: none;
border: 1px #dadada solid;
}
#checkboxes label {
display: block;
}
#checkboxes label:hover {
background-color: #1e90ff;
}<form>
<div class="multiselect">
<div class="selectBox" onclick="showCheckboxes()">
<select>
<option>Select an option</option>
</select>
<div class="overSelect"></div>
</div>
<div id="checkboxes">
<label for="one">
<input type="checkbox" id="one" />First checkbox</label>
<label for="two">
<input type="checkbox" id="two" />Second checkbox</label>
<label for="three">
<input type="checkbox" id="three" />Third checkbox</label>
</div>
</div>
</form>【讨论】：
您始终可以使用带有选择标签的 multiple 或 multiple = "true" 选项，但是有一个jquery 插件使它更漂亮。它被称为选择，可以找到here。
This fiddle-example might help you to get started
谢谢。
【讨论】：
我不得不提前说，Naveen的回答让我深受启发，所以我根据回答创建了自己的解决方案。
以下 3 个函数是我们多选的基础：
一些改进包括：
bootstrap 5
我还尝试坚持使用原生 JS（没有 jQuery）并尽可能多地使用原生 Bootstrap 5 样式
这是视频：
我无意制作适合每个人需求的即用型解决方案，因此请根据自己的喜好进行调整。我个人期待添加搜索功能。
小提琴：
window.onload = (event) => {
initMultiselect();
};
function initMultiselect() {
checkboxStatusChange();
document.addEventListener("click", function(evt) {
var flyoutElement = document.getElementById('myMultiselect'),
targetElement = evt.target; // clicked element
do {
if (targetElement == flyoutElement) {
// This is a click inside. Do nothing, just return.
//console.log('click inside');
return;
}
// Go up the DOM
targetElement = targetElement.parentNode;
} while (targetElement);
// This is a click outside.
toggleCheckboxArea(true);
//console.log('click outside');
});
}
function checkboxStatusChange() {
var multiselect = document.getElementById("mySelectLabel");
var multiselectOption = multiselect.getElementsByTagName('option')[0];
var values = [];
var checkboxes = document.getElementById("mySelectOptions");
var checkedCheckboxes = checkboxes.querySelectorAll('input[type=checkbox]:checked');
for (const item of checkedCheckboxes) {
var checkboxValue = item.getAttribute('value');
values.push(checkboxValue);
}
var dropdownValue = "Nothing is selected";
if (values.length > 0) {
dropdownValue = values.join(', ');
}
multiselectOption.innerText = dropdownValue;
}
function toggleCheckboxArea(onlyHide = false) {
var checkboxes = document.getElementById("mySelectOptions");
var displayValue = checkboxes.style.display;
if (displayValue != "block") {
if (onlyHide == false) {
checkboxes.style.display = "block";
}
} else {
checkboxes.style.display = "none";
}
}.multiselect {
width: 100%;
}
.selectBox {
position: relative;
}
.selectBox select {
width: 100%;
}
.overSelect {
position: absolute;
left: 0;
right: 0;
top: 0;
bottom: 0;
}
#mySelectOptions {
display: none;
border: 0.5px #7c7c7c solid;
background-color: #ffffff;
max-height: 150px;
overflow-y: scroll;
}
#mySelectOptions label {
display: block;
font-weight: normal;
display: block;
white-space: nowrap;
min-height: 1.2em;
background-color: #ffffff00;
padding: 0 2.25rem 0 .75rem;
/* padding: .375rem 2.25rem .375rem .75rem; */
}
#mySelectOptions label:hover {
background-color: #1e90ff;
}<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.min.js"></script>
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/css/bootstrap.min.css" rel="stylesheet"/>
<div class="container-fluid">
<div class="form-group col-sm-8">
<label for="dur">BS original select</label>
<select id="dur" class="form-select">
<option value="12" selected>One Year</option>
<option value="24">Two Year</option>
<option value="36">Three Year</option>
<option value="48">Four year</option>
<option value="60">Five Year</option>
</select>
</div>
<div class="form-group col-sm-8">
<label for="myMultiselect">BS custom multiselect</label>
<div id="myMultiselect" class="multiselect">
<div id="mySelectLabel" class="selectBox" onclick="toggleCheckboxArea()">
<select class="form-select">
<option>somevalue</option>
</select>
<div class="overSelect"></div>
</div>
<div id="mySelectOptions">
<label for="one"><input type="checkbox" id="one" onchange="checkboxStatusChange()" value="one" /> First checkbox</label>
<label for="two"><input type="checkbox" id="two" onchange="checkboxStatusChange()" value="two" /> Second checkbox</label>
<label for="three"><input type="checkbox" id="three" onchange="checkboxStatusChange()" value="three" /> Third checkbox</label>
<label for="four"><input type="checkbox" id="four" onchange="checkboxStatusChange()" value="four" /> Third checkbox</label>
<label for="five"><input type="checkbox" id="five" onchange="checkboxStatusChange()" value="five" /> First checkbox</label>
<label for="six"><input type="checkbox" id="six" onchange="checkboxStatusChange()" value="six" /> Second checkbox</label>
<label for="seven"><input type="checkbox" id="seven" onchange="checkboxStatusChange()" value="seven" /> Third checkbox</label>
<label for="eight"><input type="checkbox" id="eight" onchange="checkboxStatusChange()" value="eight" /> First checkbox</label>
<label for="nine"><input type="checkbox" id="nine" onchange="checkboxStatusChange()" value="nine" /> Second checkbox</label>
<label for="ten"><input type="checkbox" id="ten" onchange="checkboxStatusChange()" value="ten" /> Third checkbox</label>
</div>
</div>
</div>
</div>【讨论】：
使用 Bootstrap 和 JQuery 的非常简单的代码，无需任何额外的 javascript 代码：
HTML：
<div class="dropdown">
<button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Dropdown button
</button>
<form class="dropdown-menu" aria-labelledby="dropdownMenuButton">
<label class="dropdown-item"><input type="checkbox" name="" value="one">First checkbox</label>
<label class="dropdown-item"><input type="checkbox" name="" value="two">Second checkbox</label>
<label class="dropdown-item"><input type="checkbox" name="" value="three">Third checkbox</label>
</form>
</div>
CSS：
.dropdown-menu label {
display: block;
}
【讨论】：
带有复选框和 jQuery 的多个下拉菜单。
<div id="list3" class="dropdown-check-list" tabindex="100">
<span class="anchor">Which development(s) are you interested in?</span>
<ul class="items">
<li><input id="answers_2529_the-lawns" name="answers[2529][answers][]" type="checkbox" value="The Lawns"/><label for="answers_2529_the-lawns">The Lawns</label></li>
<li><input id="answers_2529_the-residence" name="answers[2529][answers][]" type="checkbox" value="The Residence"/><label for="answers_2529_the-residence">The Residence</label></li>
</ul>
</div>
<style>
.dropdown-check-list{
display: inline-block;
width: 100%;
}
.dropdown-check-list:focus{
outline:0;
}
.dropdown-check-list .anchor {
width: 98%;
position: relative;
cursor: pointer;
display: inline-block;
padding-top:5px;
padding-left:5px;
padding-bottom:5px;
border:1px #ccc solid;
}
.dropdown-check-list .anchor:after {
position: absolute;
content: "";
border-left: 2px solid black;
border-top: 2px solid black;
padding: 5px;
right: 10px;
top: 20%;
-moz-transform: rotate(-135deg);
-ms-transform: rotate(-135deg);
-o-transform: rotate(-135deg);
-webkit-transform: rotate(-135deg);
transform: rotate(-135deg);
}
.dropdown-check-list .anchor:active:after {
right: 8px;
top: 21%;
}
.dropdown-check-list ul.items {
padding: 2px;
display: none;
margin: 0;
border: 1px solid #ccc;
border-top: none;
}
.dropdown-check-list ul.items li {
list-style: none;
}
.dropdown-check-list.visible .anchor {
color: #0094ff;
}
.dropdown-check-list.visible .items {
display: block;
}
</style>
<script>
jQuery(function ($) {
var checkList = $('.dropdown-check-list');
checkList.on('click', 'span.anchor', function(event){
var element = $(this).parent();
if ( element.hasClass('visible') )
{
element.removeClass('visible');
}
else
{
element.addClass('visible');
}
});
});
</script>
【讨论】：
只需使用 bootstrap-multiselect，您就可以使用多选选项和更多功能填充下拉列表。
有关文档和教程，您可以访问以下链接
【讨论】：