Make drop-down menu multi-level

Question

I have a dropdown menu that looks like this:

.dropdown
{
    display: inline-block;
    position: relative;
}
.dropdown button > a
{
    display: block;
    color: #000000;
    text-decoration: none;
}
.dropdown-content
{
    display: none;
    position: absolute;
    width: auto;
    overflow: auto;
    box-shadow: 0px 10px 10px 0px rgba(0,0,0,0.4);
}
.dropdown:hover .dropdown-content
{
    display: block;
}
.dropdown-content a
{
    display: block;
    color: #000000;
    background-color: #e9e9ed;
    padding: 5px;
    text-decoration: none;
}
.dropdown-content a:hover
{
    color: #FFFFFF;
    background-color: #0080bf;
}

<DIV class="dropdown"><BUTTON>Menu</BUTTON><DIV class="dropdown-content">
    <A href="/1.php">Option 1</A>
    <A href="/2.php">Option 2</A>
    <A href="/3.php">Option 3</A>
    <DIV class="dropdown"><BUTTON><A href="/4.php">Option 4</A></BUTTON><DIV class="dropdown-content">
        <A href="/4-1.php">Option 4-1</A>
        <A href="/4-2.php">Option 4-2</A>
        <A href="/4-3.php">Option 4-3</A>
    </DIV></DIV>
</DIV></DIV>

But the second level menu doesn't work (press "Run Code Snippet" to see it). I need it to appear on the right side of the first level, and the width of each level must be elastic (increase and decrease automatically based on the content). Additionally, the width of the root button must not be bound to the width of the first level. Ideally any level should have a common style, but it doesn't matter since I don't have dozens of levels. Is there any solution without rewriting all the code?

Answer 1

function showNestedDropdown() {
          var firstDropdown = document.getElementById("firstDropdown");
          var nestedDropdownContainer = document.getElementById("nestedDropdownContainer");
      
          if (firstDropdown.value !== "") {
            nestedDropdownContainer.style.display = "block";
          } else {
            nestedDropdownContainer.style.display = "none";
          }
        }

    <select id="firstDropdown" onchange="showNestedDropdown()">
        <option value="">Select an option</option>
        <option value="option1">Option 1</option>
        <option value="option2">Option 2</option>
      </select>
      
      <div id="nestedDropdownContainer" style="display: none;">
        <select id="nestedDropdown">
          <option value="">Select a nested option</option>
          <option value="nested1">Nested Option 1</option>
          <option value="nested2">Nested Option 2</option>
        </select>
      </div>

Answer 2

You can do the following:

Remove overflow: auto; from .dropdown-content so that overflowed sublevels are visible. Add the > selector in the .dropdown:hover .dropdown-content line so that the direct children will be shown on hover. The last thing is to add the sublevel style to show it in the top right corner .dropdown-content .dropdown-content { left: 100%; top: 0; }

body {
  background-color: antiquewhite;
}
.dropdown
{
    display: inline-block;
    position: relative;
    width: 100%;
}
.dropdown-content
{
    display: none;
    position: absolute;
    width: auto;
    box-shadow: 0px 10px 10px 0px rgba(0,0,0,0.4);
    white-space: nowrap;
}
.dropdown:hover > .dropdown-content
{
    display: block;
}
.dropdown-content a
{
    display: block;
    color: #000000;
    background-color: #e9e9ed;
    padding: 5px;
    text-decoration: none;
}
.dropdown-content a:hover
{
    color: #FFFFFF;
    background-color: #0080bf;
}

/* To display second level on right*/
.dropdown-content .dropdown-content {
    left: 100%;
    top: 0;
}

<div class="dropdown">
    <div class="menu">Menu</div>
    <div class="dropdown-content">
      <a href="/1.php">Option 1 Longer</a>
      <div class="dropdown">
          <div class="menu">
            <a href="/4.php">Option</a>
          </div>
          <div class="dropdown-content">
            <a href="/4-1.php">Option 4-1</a>
            <a href="/4-2.php">Option 4-2</a>
            <a href="/4-3.php">Option 4-3</a>
        </div>
      </div>
    </div>
</div>