Preklopite kontekstualne prekrivke za prikaz seznamov povezav in več s spustnim vtičnikom Bootstrap.
Pregled
Spustni meniji so preklopni, kontekstualni prekrivki za prikazovanje seznamov povezav in več. Interaktivni so z vključenim spustnim vtičnikom Bootstrap JavaScript. Preklopijo se s klikom, ne z lebdenjem; to je namerna oblikovalska odločitev.
Spustni meniji so zgrajeni na podlagi knjižnice tretje osebe, Popper.js , ki zagotavlja dinamično pozicioniranje in zaznavanje vidnega polja. Ne pozabite vključiti popper.min.js pred JavaScript Bootstrapa ali uporabite bootstrap.bundle.min.js/ bootstrap.bundle.js, ki vsebuje Popper.js. Popper.js se ne uporablja za pozicioniranje spustnih menijev v vrsticah za krmarjenje, čeprav dinamično pozicioniranje ni potrebno.
Če gradite naš JavaScript iz izvorne kode, zahtevautil.js .
Dostopnost
Standard WAI ARIA definira dejanski role="menu"gradnik , vendar je to specifično za menije, podobne aplikacijam, ki sprožijo dejanja ali funkcije. Meniji ARIA lahko vsebujejo samo menijske elemente, menijske elemente potrditvenih polj, menijske elemente izbirnih gumbov, skupine izbirnih gumbov in podmenije.
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.
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:
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.
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.
You can also create non-interactive dropdown items with .dropdown-item-text. Feel free to style further with custom CSS or text utilities.
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.
Heads up! Dropdowns are positioned thanks to Popper.js (except when they are contained in a navbar).
Menu content
Headers
Add a header to label sections of actions in any dropdown menu.
Place any freeform text within a dropdown menu with text and use spacing utilities. Note that you’ll likely need additional sizing styles to constrain the menu width.
Some example text that's free-flowing within the dropdown menu.
And this is more example text.
Forms
Put a form within a dropdown menu, or make it into a dropdown menu, and use margin or padding utilities to give it the negative space you require.
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.
On touch-enabled devices, opening a dropdown adds empty ($.noop) 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.
Via data attributes
Add data-toggle="dropdown" to a link or button to toggle a dropdown.
Via JavaScript
Call the dropdowns via JavaScript:
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.
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. 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.
Note when boundary is set to any value other than 'scrollParent', the style position: static is applied to the .dropdown container.
Methods
Method
Description
$().dropdown('toggle')
Toggles the dropdown menu of a given navbar or tabbed navigation.
$().dropdown('update')
Updates the position of an element’s dropdown.
$().dropdown('dispose')
Destroys an element’s dropdown.
Events
Vsi spustni dogodki se sprožijo pri .dropdown-menunadrejenem elementu in imajo relatedTargetlastnost, katere vrednost je preklopni sidrni element. hide.bs.dropdownin hidden.bs.dropdowndogodki imajo clickEventlastnost (samo če je prvotni tip dogodka click), ki vsebuje objekt dogodka za dogodek klika.
Dogodek
Opis
show.bs.dropdown
Ta dogodek se sproži takoj, ko se pokliče metoda show instance.
shown.bs.dropdown
Ta dogodek se sproži, ko je spustni meni viden uporabniku (čakal bo na prehode CSS, da se dokončajo).
hide.bs.dropdown
Ta dogodek se sproži takoj, ko je bila poklicana metoda hide instance.
hidden.bs.dropdown
Ta dogodek se sproži, ko spustni meni ni več skrit pred uporabnikom (čakal bo na dokončanje prehodov CSS).