rooty/Bootstrap
0
0
Fork 0
mirror of https://github.com/twbs/bootstrap.git synced 2024-12-04 16:24:22 +01:00
Code Issues Actions Packages Releases Activity
7ce29d75f3
Bootstrap/site/content/docs/4.3/components/dropdowns.md
XhmikosR 98c4598696 Fix redirected links.
2020-03-24 22:05:26 +02:00

39 KiB
Raw Blame History

layout title description group toc
docs Dropdowns Toggle contextual overlays for displaying lists of links and more with the Bootstrap dropdown plugin. components true

Overview

Dropdowns are toggleable, contextual overlays for displaying lists of links and more. They're made interactive with the included Bootstrap dropdown JavaScript plugin. They're toggled by clicking, not by hovering; this is an intentional design decision.

Dropdowns are built on a third party library, Popper.js, which provides dynamic positioning and viewport detection. Be sure to include [popper.min.js]({{< param "cdn.popper" >}}) before Bootstrap's JavaScript or use bootstrap.bundle.min.js / bootstrap.bundle.js which contains Popper.js. Popper.js isn't used to position dropdowns in navbars though as dynamic positioning isn't required.

Accessibility

The WAI ARIA standard defines an actual role="menu" widget, but this is specific to application-like menus which trigger actions or functions. ARIA menus can only contain menu items, checkbox menu items, radio button menu items, radio button groups, and sub-menus.

Bootstrap's dropdowns, on the other hand, are designed to be generic and applicable to a variety of situations and markup structures. For instance, it is possible to create dropdowns that contain additional inputs and form controls, such as search fields or login forms. For this reason, Bootstrap does not expect (nor automatically add) any of the role and aria- attributes required for true ARIA menus. Authors will have to include these more specific attributes themselves.

However, Bootstrap does add built-in support for most standard keyboard menu interactions, such as the ability to move through individual .dropdown-item elements using the cursor keys and close the menu with the ESC key.

Examples

Wrap the dropdown's toggle (your button or link) and the dropdown menu within .dropdown, or another element that declares position: relative;. Dropdowns can be triggered from <a> or <button> elements to better fit your potential needs. The examples shown here use semantic <ul> elements where appropriate, but custom markup is supported.

Single button

Any single .btn can be turned into a dropdown toggle with some markup changes. Here's how you can put them to work with either <button> elements:

{{< example >}}

{{< /example >}}

And with <a> elements:

{{< example >}}

{{< /example >}}

The best part is you can do this with any button variant, too:

{{< highlight html >}}

{{< /highlight >}}

Split button

Similarly, create split button dropdowns with virtually the same markup as single button dropdowns, but with the addition of .dropdown-toggle-split for proper spacing around the dropdown caret.

We use this extra class to reduce the horizontal padding on either side of the caret by 25% and remove the margin-left that's added for regular button dropdowns. Those extra changes keep the caret centered in the split button and provide a more appropriately sized hit area next to the main button.

{{< highlight html >}}

{{< /highlight >}}

Sizing

Button dropdowns work with buttons of all sizes, including default and split dropdown buttons.

{{< highlight html >}}

Large button
    ...
Large split button Toggle Dropdown
    ...
Small button
    ...
Small split button Toggle Dropdown
    ...
{{< /highlight >}}

Directions

Dropup

Trigger dropdown menus above elements by adding .dropup to the parent element.

{{< highlight html >}}

Dropup
Split dropup Toggle Dropdown
{{< /highlight >}}

Dropright

Trigger dropdown menus at the right of the elements by adding .dropright to the parent element.

{{< highlight html >}}

Dropright
Split dropright Toggle Dropright
{{< /highlight >}}

Dropleft

Trigger dropdown menus at the left of the elements by adding .dropleft to the parent element.

{{< highlight html >}}

Dropleft
Toggle Dropleft
Split dropleft
{{< /highlight >}}

Menu items

Historically dropdown menu contents had to be links, but that's no longer the case with v4. Now you can optionally use <button> elements in your dropdowns instead of just <a>s.

{{< example >}}

Dropdown
  • Action
  • Another action
  • Something else here
{{< /example >}}

You can also create non-interactive dropdown items with .dropdown-item-text. Feel free to style further with custom CSS or text utilities.

{{< example >}}

{{< /example >}}

Active

Add .active to items in the dropdown to style them as active. To convey the active state to assistive technologies, use the aria-current attribute — using the page value for the current page, or true for the current item in a set.

{{< example >}}

{{< /example >}}

Disabled

Add .disabled to items in the dropdown to style them as disabled.

{{< example >}}

{{< /example >}}

Menu alignment

By default, a dropdown menu is automatically positioned 100% from the top and along the left side of its parent. Add .dropdown-menu-right to a .dropdown-menu to right align the dropdown menu.

{{< callout info >}} Heads up! Dropdowns are positioned thanks to Popper.js (except when they are contained in a navbar). {{< /callout >}}

{{< example >}}

Right-aligned menu
  • Action
  • Another action
  • Something else here
{{< /example >}}

Responsive alignment

If you want to use responsive alignment, disable dynamic positioning by adding the data-display="static" attribute and use the responsive variation classes.

To align right the dropdown menu with the given breakpoint or larger, add .dropdown-menu{-sm|-md|-lg|-xl}-right.

{{< example >}}

Left-aligned but right aligned when large screen
  • Action
  • Another action
  • Something else here
{{< /example >}}

To align left the dropdown menu with the given breakpoint or larger, add .dropdown-menu-right and .dropdown-menu{-sm|-md|-lg|-xl}-left.

{{< example >}}

Right-aligned but left aligned when large screen
  • Action
  • Another action
  • Something else here
{{< /example >}}

Note that you don't need to add a data-display="static" attribute to dropdown buttons in navbars, since Popper.js isn't used in navbars.

Menu content

Headers

Add a header to label sections of actions in any dropdown menu.

{{< example >}}

{{< /example >}}

Dividers

Separate groups of related menu items with a divider.

{{< example >}}

{{< /example >}}

Text

Place any freeform text within a dropdown menu with text and use [spacing utilities]({{< docsref "/utilities/spacing" >}}). Note that you'll likely need additional sizing styles to constrain the menu width.

{{< example >}}

Some example text that's free-flowing within the dropdown menu.

And this is more example text.

{{< /example >}}

Forms

Put a form within a dropdown menu, or make it into a dropdown menu, and use [margin or padding utilities]({{< docsref "/utilities/spacing" >}}) to give it the negative space you require.

{{< example >}}

Sign in
New around here? Sign up Forgot password?
{{< /example >}}

{{< example >}}

Sign in {{< /example >}}

Dropdown options

Use data-offset or data-reference to change the location of the dropdown.

{{< example >}}

{{< /example >}}

Usage

Via data attributes or JavaScript, the dropdown plugin toggles hidden content (dropdown menus) by toggling the .show class on the parent list item. The data-toggle="dropdown" attribute is relied on for closing dropdown menus at an application level, so it's a good idea to always use it.

{{< callout info >}} On touch-enabled devices, opening a dropdown adds empty mouseover handlers to the immediate children of the <body> element. This admittedly ugly hack is necessary to work around a quirk in iOS' event delegation, which would otherwise prevent a tap anywhere outside of the dropdown from triggering the code that closes the dropdown. Once the dropdown is closed, these additional empty mouseover handlers are removed. {{< /callout >}}

Via data attributes

Add data-toggle="dropdown" to a link or button to toggle a dropdown.

{{< highlight html >}}

Dropdown trigger
    ...
{{< /highlight >}}

Via JavaScript

Call the dropdowns via JavaScript:

{{< highlight js >}} var dropdownElementList = [].slice.call(document.querySelectorAll('.dropdown-toggle')) var dropdownList = dropdownElementList.map(function (dropdownToggleEl) { return new bootstrap.Dropdown(dropdownToggleEl) }) {{< /highlight >}}

{{< callout info >}}

data-toggle="dropdown" still required

Regardless of whether you call your dropdown via JavaScript or instead use the data-api, data-toggle="dropdown" is always required to be present on the dropdown's trigger element. {{< /callout >}}

Options

Options can be passed via data attributes or JavaScript. For data attributes, append the option name to data-, as in data-offset="".

Name Type Default Description
offset number | string | function 0

Offset of the dropdown relative to its target.

When a function is used to determine the offset, it is called with an object containing the offset data as its first argument. The function must return an object with the same structure. The triggering element DOM node is passed as the second argument.

For more information refer to Popper.js's offset docs.
flip boolean true Allow Dropdown to flip in case of an overlapping on the reference element. For more information refer to Popper.js's flip docs.
boundary string | element 'scrollParent' Overflow constraint boundary of the dropdown menu. Accepts the values of 'viewport', 'window', 'scrollParent', or an HTMLElement reference (JavaScript only). For more information refer to Popper.js's preventOverflow docs.
reference string | element 'toggle' Reference element of the dropdown menu. Accepts the values of 'toggle', 'parent', or an HTMLElement reference. For more information refer to Popper.js's referenceObject docs.
display string 'dynamic' By default, we use Popper.js for dynamic positioning. Disable this with static.
popperConfig null | object null To change Bootstrap's default Popper.js config, see Popper.js's configuration

Note when boundary is set to any value other than 'scrollParent', the style position: static is applied to the .dropdown container.

Methods

Method Description
toggle Toggles the dropdown menu of a given navbar or tabbed navigation.
show Shows the dropdown menu of a given navbar or tabbed navigation.
hide Hides the dropdown menu of a given navbar or tabbed navigation.
update Updates the position of an element's dropdown.
dispose Destroys an element's dropdown.
getInstance Static method which allows you to get the dropdown instance associated with a DOM element.

Events

All dropdown events are fired at the .dropdown-menu's parent element and have a relatedTarget property, whose value is the toggling anchor element. hide.bs.dropdown and hidden.bs.dropdown events have a clickEvent property (only when the original Event type is click) that contains an Event Object for the click event.

Method Description
show.bs.dropdown Fires immediately when the show instance method is called.
shown.bs.dropdown Fired when the dropdown has been made visible to the user and CSS transitions have completed.
hide.bs.dropdown Fires immediately when the hide instance method has been called.
hidden.bs.dropdown Fired when the dropdown has finished being hidden from the user and CSS transitions have completed.

{{< highlight js >}} var myDropdown = document.getElementById('myDropdown') myDropdown.addEventListener('show.bs.dropdown', function () { // do something... }) {{< /highlight >}}