我需要做的是在一个选择框中，当用户选择一个选项时，在选中的选项之后会出现一个绿色的标记，表示欢迎所有建议
答案 0 :(得分：0)
欢迎堆栈溢出！
您应该始终尝试研究，因为我很容易在https://www.w3schools.com/howto/howto_css_custom_checkbox.asp上找到了解决方案，这是结果的第一页。
下面是代码：
<!DOCTYPE html>
<html>
<style>
/* The container */
.container {
display: block;
position: relative;
padding-left: 35px;
margin-bottom: 12px;
cursor: pointer;
font-size: 22px;
-webkit-user-select: none;
-moz-user-select: none;
-ms-user-select: none;
user-select: none;
}
/* Hide the browser's default checkbox */
.container input {
position: absolute;
opacity: 0;
cursor: pointer;
}
/* Create a custom checkbox */
.checkmark {
position: absolute;
top: 0;
left: 0;
height: 25px;
width: 25px;
background-color: #eee;
}
/* On mouse-over, add a grey background color */
.container:hover input ~ .checkmark {
background-color: #ccc;
}
.container input:checked ~ .checkmark {
background-color: green; /* The only code I edited */
}
/* Create the checkmark/indicator (hidden when not checked) */
.checkmark:after {
content: "";
position: absolute;
display: none;
}
/* Show the checkmark when checked */
.container input:checked ~ .checkmark:after {
display: block;
}
/* Style the checkmark/indicator */
.container .checkmark:after {
left: 9px;
top: 5px;
width: 5px;
height: 10px;
border: solid white;
border-width: 0 3px 3px 0;
-webkit-transform: rotate(45deg);
-ms-transform: rotate(45deg);
transform: rotate(45deg);
}
</style>
<body>
<h1>Custom Checkboxes</h1>
<label class="container">One
<input type="checkbox" checked="checked">
<span class="checkmark"></span>
</label>
<label class="container">Two
<input type="checkbox">
<span class="checkmark"></span>
</label>
<label class="container">Three
<input type="checkbox">
<span class="checkmark"></span>
</label>
<label class="container">Four
<input type="checkbox">
<span class="checkmark"></span>
</label>
</body>
</html>
我所做的就是从https://www.w3schools.com/howto/tryit.asp?filename=tryhow_css_custom_checkbox复制代码。
然后，我把代码弄乱了一段时间，直到看到背景色：蓝色，然后将其更改为绿色。
哦，等等，这不是您的问题！您希望在选择框上显示它。很好，因为您可以在select上使用很多CSS。只需稍微摆弄代码即可。
这里有个例子：
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
/*the container must be positioned relative:*/
.custom-select {
position: relative;
font-family: Arial;
}
.custom-select select {
display: none; /*hide original SELECT element:*/
}
.select-selected {
background-color: DodgerBlue;
}
/*style the arrow inside the select element:*/
.select-selected:after {
position: absolute;
content: "";
top: 14px;
right: 10px;
width: 0;
height: 0;
border: 6px solid transparent;
border-color: #fff transparent transparent transparent;
}
/*point the arrow upwards when the select box is open (active):*/
.select-selected.select-arrow-active:after {
border-color: transparent transparent #fff transparent;
top: 7px;
}
/*style the items (options), including the selected item:*/
.select-items div,.select-selected {
color: #ffffff;
padding: 8px 16px;
border: 1px solid transparent;
border-color: transparent transparent rgba(0, 0, 0, 0.1) transparent;
cursor: pointer;
user-select: none;
}
/*style items (options):*/
.select-items {
position: absolute;
background-color: DodgerBlue;
top: 100%;
left: 0;
right: 0;
z-index: 99;
}
.select-selected:after{
left: 9px;
top: 5px;
width: 5px;
height: 10px;
border: solid white;
border-width: 0 3px 3px 0;
-webkit-transform: rotate(45deg);
-ms-transform: rotate(45deg);
transform: rotate(45deg);
}
/*hide the items when the select box is closed:*/
.select-hide {
display: none;
}
.select-items div:hover, .same-as-selected {
background-color: rgba(0, 0, 0, 0.1);
}
</style>
</head>
<body>
<h2>Custom Select</h2>
<!--surround the select box with a "custom-select" DIV element. Remember to set the width:-->
<div class="custom-select" style="width:200px;">
<select>
<option value="0">Select:</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
</div>
<script>
var x, i, j, selElmnt, a, b, c;
/*look for any elements with the class "custom-select":*/
x = document.getElementsByClassName("custom-select");
for (i = 0; i < x.length; i++) {
selElmnt = x[i].getElementsByTagName("select")[0];
/*for each element, create a new DIV that will act as the selected item:*/
a = document.createElement("DIV");
a.setAttribute("class", "select-selected");
a.innerHTML = selElmnt.options[selElmnt.selectedIndex].innerHTML;
x[i].appendChild(a);
/*for each element, create a new DIV that will contain the option list:*/
b = document.createElement("DIV");
b.setAttribute("class", "select-items select-hide");
for (j = 0; j < selElmnt.length; j++) {
/*for each option in the original select element,
create a new DIV that will act as an option item:*/
c = document.createElement("DIV");
c.innerHTML = selElmnt.options[j].innerHTML;
c.addEventListener("click", function(e) {
/*when an item is clicked, update the original select box,
and the selected item:*/
var y, i, k, s, h;
s = this.parentNode.parentNode.getElementsByTagName("select")[0];
h = this.parentNode.previousSibling;
for (i = 0; i < s.length; i++) {
if (s.options[i].innerHTML == this.innerHTML) {
s.selectedIndex = i;
h.innerHTML = this.innerHTML;
y = this.parentNode.getElementsByClassName("same-as-selected");
for (k = 0; k < y.length; k++) {
y[k].removeAttribute("class");
}
this.setAttribute("class", "same-as-selected");
break;
}
}
h.click();
});
b.appendChild(c);
}
x[i].appendChild(b);
a.addEventListener("click", function(e) {
/*when the select box is clicked, close any other select boxes,
and open/close the current select box:*/
e.stopPropagation();
closeAllSelect(this);
this.nextSibling.classList.toggle("select-hide");
this.classList.toggle("select-arrow-active");
});
}
function closeAllSelect(elmnt) {
/*a function that will close all select boxes in the document,
except the current select box:*/
var x, y, i, arrNo = [];
x = document.getElementsByClassName("select-items");
y = document.getElementsByClassName("select-selected");
for (i = 0; i < y.length; i++) {
if (elmnt == y[i]) {
arrNo.push(i)
} else {
y[i].classList.remove("select-arrow-active");
}
}
for (i = 0; i < x.length; i++) {
if (arrNo.indexOf(i)) {
x[i].classList.add("select-hide");
}
}
}
/*if the user clicks anywhere outside the select box,
then close all select boxes:*/
document.addEventListener("click", closeAllSelect);</script>
</body>
</html>
是白色的？是的，需要使其绿色！只需执行与第一个示例完全相同的操作即可！自我解释，或者基本上是这样：
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
/*the container must be positioned relative:*/
.custom-select {
position: relative;
font-family: Arial;
}
.custom-select select {
display: none; /*hide original SELECT element:*/
}
.select-selected {
background-color: DodgerBlue;
}
/*style the arrow inside the select element:*/
.select-selected:after {
position: absolute;
content: "";
top: 14px;
right: 10px;
width: 0;
height: 0;
border: 6px solid transparent;
border-color: #fff transparent transparent transparent;
}
/*point the arrow upwards when the select box is open (active):*/
.select-selected.select-arrow-active:after {
border-color: transparent transparent #fff transparent;
top: 7px;
}
/*style the items (options), including the selected item:*/
.select-items div,.select-selected {
color: #ffffff;
padding: 8px 16px;
border: 1px solid transparent;
border-color: transparent transparent rgba(0, 0, 0, 0.1) transparent;
cursor: pointer;
user-select: none;
}
/*style items (options):*/
.select-items {
position: absolute;
background-color: DodgerBlue;
top: 100%;
left: 0;
right: 0;
z-index: 99;
}
.select-selected:after{
left: 7px;
top: 10px;
width: 5px;
height: 10px;
border: solid green;
border-width: 0 3px 3px 0;
-webkit-transform: rotate(45deg);
-ms-transform: rotate(45deg);
transform: rotate(45deg);
color: green;
}
/*hide the items when the select box is closed:*/
.select-hide {
display: none;
}
.select-items div:hover, .same-as-selected {
background-color: rgba(0, 0, 0, 0.1);
}
</style>
</head>
<body>
<h2>Custom Select</h2>
<!--surround the select box with a "custom-select" DIV element. Remember to set the width:-->
<div class="custom-select" style="width:200px;">
<select>
<option value="0">Select:</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
</div>
<script>
var x, i, j, selElmnt, a, b, c;
/*look for any elements with the class "custom-select":*/
x = document.getElementsByClassName("custom-select");
for (i = 0; i < x.length; i++) {
selElmnt = x[i].getElementsByTagName("select")[0];
/*for each element, create a new DIV that will act as the selected item:*/
a = document.createElement("DIV");
a.setAttribute("class", "select-selected");
a.innerHTML = selElmnt.options[selElmnt.selectedIndex].innerHTML;
x[i].appendChild(a);
/*for each element, create a new DIV that will contain the option list:*/
b = document.createElement("DIV");
b.setAttribute("class", "select-items select-hide");
for (j = 0; j < selElmnt.length; j++) {
/*for each option in the original select element,
create a new DIV that will act as an option item:*/
c = document.createElement("DIV");
c.innerHTML = selElmnt.options[j].innerHTML;
c.addEventListener("click", function(e) {
/*when an item is clicked, update the original select box,
and the selected item:*/
var y, i, k, s, h;
s = this.parentNode.parentNode.getElementsByTagName("select")[0];
h = this.parentNode.previousSibling;
for (i = 0; i < s.length; i++) {
if (s.options[i].innerHTML == this.innerHTML) {
s.selectedIndex = i;
h.innerHTML = this.innerHTML;
y = this.parentNode.getElementsByClassName("same-as-selected");
for (k = 0; k < y.length; k++) {
y[k].removeAttribute("class");
}
this.setAttribute("class", "same-as-selected");
break;
}
}
h.click();
});
b.appendChild(c);
}
x[i].appendChild(b);
a.addEventListener("click", function(e) {
/*when the select box is clicked, close any other select boxes,
and open/close the current select box:*/
e.stopPropagation();
closeAllSelect(this);
this.nextSibling.classList.toggle("select-hide");
this.classList.toggle("select-arrow-active");
});
}
function closeAllSelect(elmnt) {
/*a function that will close all select boxes in the document,
except the current select box:*/
var x, y, i, arrNo = [];
x = document.getElementsByClassName("select-items");
y = document.getElementsByClassName("select-selected");
for (i = 0; i < y.length; i++) {
if (elmnt == y[i]) {
arrNo.push(i)
} else {
y[i].classList.remove("select-arrow-active");
}
}
for (i = 0; i < x.length; i++) {
if (arrNo.indexOf(i)) {
x[i].classList.add("select-hide");
}
}
}
/*if the user clicks anywhere outside the select box,
then close all select boxes:*/
document.addEventListener("click", closeAllSelect);</script>
</body>
</html>
祝您好运！只需记住下一次研究，然后再发布问题。
来源：
答案 1 :(得分：0)
你是这个意思吗？
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;
padding: 5px;
border: 1px #dadada solid;
}
#checkboxes label:hover {
background-color: #1e90ff;
}
input[type="checkbox"]:checked+label::after {
content: '';
position: absolute;
width: 1.2ex;
height: 0.4ex;
background: rgba(0, 0, 0, 0);
top: 0.9ex;
right: 2px;
border: 3px solid green;
border-top: none;
border-right: none;
-webkit-transform: rotate(-45deg);
-moz-transform: rotate(-45deg);
-o-transform: rotate(-45deg);
-ms-transform: rotate(-45deg);
transform: rotate(-45deg);
}
input[type="checkbox"] {
line-height: 2.1ex;
}
input[type="radio"],
input[type="checkbox"] {
position: absolute;
left: -999em;
}
input[type="checkbox"]+label {
position: relative;
overflow: hidden;
cursor: pointer;
display: block;
width: 100%;
}<form>
<div class="multiselect">
<div class="selectBox" onclick="showCheckboxes()">
<select>
<option>Select an option</option>
</select>
<div class="overSelect"></div>
</div>
<div id="checkboxes">
<input type="checkbox" id="one" /><label for="one">First checkbox</label>
<input type="checkbox" id="two" /><label for="two">Second checkbox</label>
<input type="checkbox" id="three" /><label for="three">Third checkbox</label>
</div>
</div>
</form>