How Can I Create an Upward-Opening Drop-Down Menu Using Only CSS?

Drop-down Menu that Opens Upward with Pure CSS

Pure CSS enables the creation of robust and visually appealing drop-down menus. This tutorial will guide you through the steps to achieve an "upward" drop-down menu, which mở ra bên trên instead of the typical downward opening.

At the outset, you have established a pure CSS drop-down menu that meets your requirements except for its downward opening. Our goal is to modify your code to make the menu open upwards, thereby becoming an "drop-up" menu.

To achieve this upward opening, you need to make a slight modification to your CSS rules:

Solution 1: Adjust Positioning

In the CSS rule that positions the submenus of your drop-down menu, add the bottom: 100% property. This will essentially move the submenus above their parent menu items instead of below them.

#menu:hover ul li:hover ul {
  position: absolute;
  margin-top: 1px;
  font: 10px;
  bottom: 100%;
}

Solution 2: Target Specific Submenus

If you want to prevent the upward opening effect from applying to all submenus, you can use a more targeted CSS rule. In this case, modify the rule to target only the submenus of the top-level menu items.

#menu>ul>li:hover>ul {
  bottom: 100%;
}

Solution 3: Preserve Menu Border

If adjusting the positioning of the submenus affects their visual appearance, you can add a border-bottom property to maintain the desired look.

#menu>ul>li:hover>ul {
  bottom: 100%;
  border-bottom: 1px solid transparent;
}

By implementing one of these solutions, you can achieve the desired "drop-up" menu using pure CSS. You can find a live demonstration at http://jsfiddle.net/W5FWW/4/.

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