javascript - 单击某些列表项时如何更改 div 的值？

Question

我已经建立了一个下拉列表，但我对它并不完全满意。我正在为如何使用单击的列表项的值更改默认状态的值而苦苦挣扎。

HTML:

<div class="dropdown">
  <input class="dropdown-toggle" type="text">
  <div class="dropdown-text">Account</div>
  <ul class="dropdown-content">
    <li><a href="#">Settings</a></li>
    <li><a href="#">Projects</a></li>
    <li><a href="#">Log out</a></li>
  </ul>
</div>

我正在使用的 JS:

var ddl = document.getElementByClass('dropdown-content');
var opts = ddl.options.length;
for (var i=0; i<opts; i++){
    if (ddl.options[i].value == "some-value"){
        ddl.options[i].selected = true;
        break;
    }
}

这行不通，我不明白为什么。我是 JavaScript 的新手。我想用您在下拉列表中单击的任何内容来更改“帐户”。

这是一个 fiddle :

https://jsfiddle.net/xrqas38n/

PS:我不想使用 jQuery。

Answer 1

这是一种方法:

var current_item = document.querySelector('.dropdown-text');
var items = document.querySelectorAll('.dropdown-content > li > a');
items.forEach(function(item) {
  item.addEventListener('click', selectionChanged);
});

function selectionChanged(e) {
  e.preventDefault();
  var target = e.currentTarget;
  current_item.innerHTML = target.innerHTML;
}

a {
  text-decoration: none;
}

.dropdown {
  position: relative;
  display: inline-block;
  text-align: left;
  width: 132px;
}

.dropdown-text {
  cursor: pointer;
  position: absolute;
  text-indent: 10px;
  line-height: 32px;
  background-color: #eee;
  border: 1px solid #ccc;
  border-radius: 3px;
  box-shadow: 0 1px 0 rgba(255, 255, 255, .9) inset, 0 1px 3px rgba(0, 0, 0, .1);
  width: 100%;
}

.dropdown-text:after {
  position: absolute;
  right: 6px;
  top: 15px;
  content: '';
  width: 0px;
  height: 0px;
  border-style: solid;
  border-width: 5px 4px 0 4px;
  border-color: #555 transparent transparent transparent;
}

.dropdown-text,
.dropdown-content a {
  color: #333;
  text-shadow: 0 1px #fff;
}

.dropdown-toggle {
  font-size: 0;
  z-index: 1;
  cursor: pointer;
  position: absolute;
  top: 0;
  border: none;
  padding: 0;
  margin: 0 0 0 1px;
  background: transparent;
  text-indent: -10px;
  height: 34px;
  width: 100%;
}

.dropdown-toggle:focus {
  outline: 0;
}

.dropdown-content {
  list-style-type: none;
  position: absolute;
  top: 32px;
  padding: 0;
  margin: 0;
  opacity: 0;
  visibility: hidden;
  border-radius: 3px;
  text-indent: 10px;
  line-height: 32px;
  background-color: #eee;
  border: 1px solid #ccc;
  width: 140px;
}

.dropdown-content a {
  display: block;
}

.dropdown-content a:hover {
  background: #e8e8e8;
}

.dropdown-toggle:hover ~ .dropdown-text,
.dropdown-toggle:focus ~ .dropdown-text {
  background-color: #e8e8e8;
}

.dropdown-toggle:focus ~ .dropdown-text {
  box-shadow: 0 1px 3px rgba(0, 0, 0, .2) inset, 0 1px 0 rgba(255, 255, 255, 0.8);
  z-index: 2;
}

.dropdown-toggle:focus ~ .dropdown-text:after {
  border-width: 0 4px 5px 4px;
  border-color: transparent transparent #555 transparent;
}

.dropdown-content:hover,
.dropdown-toggle:focus ~ .dropdown-content {
  opacity: 1;
  visibility: visible;
  top: 42px;
}

<div class="dropdown">
  <input class="dropdown-toggle" type="text">
  <div class="dropdown-text">Account</div>
  <ul class="dropdown-content">
    <li><a href="#">Settings</a></li>
    <li><a href="#">Projects</a></li>
    <li><a href="#">Log out</a></li>
  </ul>
</div>