javascript - JavaScript:从下拉菜单中检索所选值的最佳方法是什么？

我只是想从下拉菜单中检索所选选项的值。我整理了一些杂乱无章的东西，几乎可以正常工作了。

什么是适合此任务的解决方案？

您会看到从下拉菜单中有四个选项值可供选择：奥迪，雪铁龙，宝马，特斯拉。我想知道从下拉列表中选择了哪个值，以便在与选择相对应的页面上显示内容。

代码如下：

// WHAT IS THE BEST WAY TO RETRIEVE THE VALUE FROM THE DROPDOWN MENU?
function pageSelected() {
if (document.getElementById("myDropdown").value == 1) {
document.getElementById("optionvalue").innerHTML = "Audi";
} else if (document.getElementById("myDropdown").value == 2) {
document.getElementById("optionvalue").innerHTML = "Citroen";
} else if (document.getElementById("myDropdown").value == 3) {
document.getElementById("optionvalue").innerHTML = "BMW";
} else if (document.getElementById("myDropdown").value == 4) {
document.getElementById("optionvalue").innerHTML = "Ford";
}
}

/* When the user clicks on the button,
toggle between hiding and showing the dropdown content */
function ddm() {
    document.getElementById("myDropdown").classList.toggle("show");
}

// Close the dropdown if the user clicks outside of it
window.onclick = function(event) {
  if (!event.target.matches('.dropbtn')) {

    var dropdowns = document.getElementsByClassName("dropdown-content");
    var i;
    for (i = 0; i < dropdowns.length; i++) {
      var openDropdown = dropdowns[i];
      if (openDropdown.classList.contains('show')) {
        openDropdown.classList.remove('show');
      }
    }
  }
}

.dropbtn {
    background-color: #3498DB;
    color: white;
    padding: 16px;
    font-size: 16px;
    border: none;
    cursor: pointer;
}

.dropbtn:hover, .dropbtn:focus {
    background-color: #2980B9;
}

.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #f1f1f1;
    min-width: 160px;
    overflow: auto;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
}

.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
}

.dropdown a:hover {background-color: #ddd;}

.show {display: block;}

<div id="infobar">
<div id="info">
</div>

<!--dropdown option value goes here-->
<div id="optionvalue">option value</div>

<div class="dropdown">
<button onclick="ddm()" class="dropbtn">&#9660;</button>
  <div id="myDropdown" class="dropdown-content">
    <a><option value="1" onclick="pageSelected()" >Audi</option></a>
    <a><option value="2" onclick="pageSelected()">Citroen</option></a>
    <a><option value="3" onclick="pageSelected()">BMW</option></a>
    <a><option value="4" onclick="pageSelected()">Ford</option></a>

  </div>
</div>

最佳答案

您可以将元素传递到pageSelected并从那里获取值

<option value="1" onclick="pageSelected(this)" >Audi</option>

function pageSelected(option) {
    document.getElementById("optionvalue").innerHTML = option.value + ' ' + option.innerHTML;
}

// WHAT IS THE BEST WAY TO RETRIEVE THE VALUE FROM THE DROPDOWN MENU?
function pageSelected(option) {
document.getElementById("optionvalue").innerHTML = option.value + ' ' + option.innerHTML;
}

/* When the user clicks on the button,
toggle between hiding and showing the dropdown content */
function ddm() {
    document.getElementById("myDropdown").classList.toggle("show");
}

// Close the dropdown if the user clicks outside of it
window.onclick = function(event) {
  if (!event.target.matches('.dropbtn')) {

    var dropdowns = document.getElementsByClassName("dropdown-content");
    var i;
    for (i = 0; i < dropdowns.length; i++) {
      var openDropdown = dropdowns[i];
      if (openDropdown.classList.contains('show')) {
        openDropdown.classList.remove('show');
      }
    }
  }
}

.dropbtn {
    background-color: #3498DB;
    color: white;
    padding: 16px;
    font-size: 16px;
    border: none;
    cursor: pointer;
}

.dropbtn:hover, .dropbtn:focus {
    background-color: #2980B9;
}

.dropdown {
    position: relative;
    display: inline-block;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #f1f1f1;
    min-width: 160px;
    overflow: auto;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
}

.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
}

.dropdown a:hover {background-color: #ddd;}

.show {display: block;}

<div id="infobar">
<div id="info">
</div>

<!--dropdown option value goes here-->
<div id="optionvalue">option value</div>

<div class="dropdown">
<button onclick="ddm()" class="dropbtn">&#9660;</button>
  <div id="myDropdown" class="dropdown-content">
    <a><option value="1" onclick="pageSelected(this)" >Audi</option></a>
    <a><option value="2" onclick="pageSelected(this)">Citroen</option></a>
    <a><option value="3" onclick="pageSelected(this)">BMW</option></a>
    <a><option value="4" onclick="pageSelected(this)">Ford</option></a>

  </div>
</div>

关于javascript - JavaScript:从下拉菜单中检索所选值的最佳方法是什么？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/53502774/