focus-trap
v8.0.0TypeScript
Trap focus within a DOM node.
0/weekUpdated 1 weeks agoMITUnpacked: 836.7 KB
Published by David Clark
npm install focus-trapfocus-trap  
Trap focus within a DOM node.
There may come a time when you find it important to trap focus within a DOM node — so that when a user hits Tab or Shift+Tab or clicks around, she can't escape a certain cycle of focusable elements.
You will definitely face this challenge when you are trying to build accessible modals.
This module is a little, modular vanilla JS solution to that problem.
Use it in your higher-level components. For example, if you are using React check out focus-trap-react, a light wrapper around this library. If you are not a React user, consider creating light wrappers in your framework-of-choice.
What it does
When a focus trap is activated, this is what should happen:
- Some element within the focus trap receives focus. By default, this will be the first element in the focus trap's tab order (as determined by tabbable). Alternately, you can specify an element that should receive this initial focus.
- The Tab and Shift+Tab keys will cycle through the focus trap's tabbable elements but will not leave the focus trap.
- Clicks within the focus trap behave normally; but clicks outside the focus trap are blocked.
- The Escape key will deactivate the focus trap.
When the focus trap is deactivated, this is what should happen:
- Focus is passed to whichever element had focus when the trap was activated (e.g. the button that opened the modal or menu).
- Tabbing and clicking behave normally everywhere.
For more advanced usage (e.g. focus traps within focus traps), you can also pause a focus trap's behavior without deactivating it entirely, then unpause at will.
Installation
``bash`
npm install focus-trap
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You can also use a UMD version published to unpkg.com as dist/focus-trap.umd.js and dist/focus-trap.umd.min.js.
> NOTE: The UMD build does not bundle the tabbable dependency. Therefore you will have to also include that one, and include it before focus-trap.
`html`
Browser Support
As old and as broad as _reasonably_ possible, excluding browsers that are out of support or have nearly no user base.
Focused on desktop browsers, particularly Chrome, Edge, FireFox, Safari, and Opera.
Focus-trap is not officially tested on any mobile browsers or devices.
> ❗️ __Safari__: By default, Safari does not tab through all elements on a page, which alters the normal DOM-based tab order expected by focus-trap. If you use or support Safari with this library, make sure you and your users know they __must enable__ the Preferences > Advanced > Press Tab to highlight each item on a webpage feature. Otherwise, your traps will not work the way you expect them to.
> ⚠️ Microsoft no longer supports any version of IE, so IE is no longer supported by this library.
> 💬 Focus-trap relies on tabbable so its browser support is at least what tabbable supports.
> 💬 Keep in mind that performance optimization and old browser support are often at odds, so tabbable may not always be able to use the most optimal (typically modern) APIs in all cases.
Usage
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`javascriptfocusTrap
import * as focusTrap from 'focus-trap'; // ESM
const focusTrap = require('focus-trap'); // CJS
// UMD: is defined as a global on window
trap = focusTrap.createFocusTrap(element[, createOptions]);
`
Returns a new focus trap on element (one or more "containers" of tabbable nodes that, together, form the total set of nodes that can be visited, with clicks or the tab key, within the trap).
element can be:
- a DOM node (the focus trap itself);
- a selector string (which will be passed to document.querySelector() to find the DOM node); or
- an array of DOM nodes or selector strings (where the order determines where the focus will go after the last tabbable element of a DOM node/selector is reached).
> A focus trap must have at least one container with at least one tabbable/focusable node in it to be considered valid. While nodes can be added/removed at runtime, with the trap adjusting to added/removed tabbable nodes, an error will be thrown if the trap ever gets into a state where it determines none of its containers have any tabbable nodes in them and the fallbackFocus option does not resolve to an alternate node where focus can go.
#### Trap Configuration Options
##### onActivate
`typescript`
() => void
A function that will be called before sending focus to the target element upon activation.
##### onPostActivate
`typescript`
() => void
A function that will be called after sending focus to the target element upon activation unless initial focus is delayed because the delayInitialFocus is true (default).
##### onPause
`typescript`
() => void
A function that will be called immediately after the trap's state is updated to be paused.
##### onPostPause
`typescript`
() => void
A function that will be called after the trap has been completely paused and is no longer managing/trapping focus.
##### onUnpause
`typescript`
() => void
A function that will be called immediately after the trap's state is updated to be active again, but prior to updating its knowledge of what nodes are tabbable within its containers, and prior to actively managing/trapping focus.
##### onPostUnpause
`typescript`
() => void
A function that will be called after the trap has been completely unpaused and is once again managing/trapping focus.
Note that if delayInitialFocus is true, this handler will be called before focus is re-set on the initial focused node.
##### checkCanFocusTrap
`typescript`
(containers: Array
Animated dialogs have a small delay between when onActivate is called and when the focus trap is focusable. checkCanFocusTrap expects a promise to be returned. When that promise settles (resolves or rejects), focus will be sent to the first tabbable node (in tab order) in the focus trap (or the node configured in the initialFocus option).
##### onDeactivate
`typescript`
() => void
A function that will be called before returning focus to the node that had focus prior to activation (or configured with the setReturnFocus option) upon deactivation.
##### onPostDeactivate
`typescript`
() => void
A function that will be called after the trap is deactivated, after onDeactivate. If the returnFocus deactivation option was set, it will be called after returning focus to the node that had focus prior to activation (or configured with the setReturnFocus option) upon deactivation; otherwise, it will be called after deactivation completes.
##### checkCanReturnFocus
`typescript`
(trigger: HTMLElement | SVGElement) => Promise
An animated trigger button will have a small delay between when onDeactivate is called and when the focus is able to be sent back to the trigger. checkCanReturnFocus expects a promise to be returned. When that promise settles (resolves or rejects), focus will be sent to to the node that had focus prior to the activation of the trap (or the node configured in the setReturnFocus option).
##### initialFocus
`typescript`
HTMLElement | SVGElement | string | false | undefined | (() => HTMLElement | SVGElement | string | false | undefined)
By default (when undefined or the function returns undefined), when a focus trap is activated, the active element will receive focus if it's in the trap, otherwise, the first element in the focus trap's tab order will receive focus. With this option you can specify a different element to receive that initial focus. Can be a DOM node, or a selector string (which will be passed to document.querySelector() to find the DOM node), or a function that returns any of these. You can also set this option to false (or to a function that returns false) to prevent any initial focus at all when the trap activates.
- Setting this option to false (or a function that returns false) will prevent the fallbackFocus option from being used.fallbackFocus
- If the option resolves to a non-focusable node (e.g. one that exists, but is hidden), the default behavior will be used (as though the option weren't set at all).
- If the option resolves to a non-existent node, an exception will be thrown.
- If the option resolves to a valid selector string (directly set, or returned from a function), but the selector doesn't match a node, the trap will fall back to the node option. If that option also fails to yield a node, an exception will be thrown.undefined
- If the option resolves to (i.e. not set or function returns undefined), the default behavior will be used.
- ⚠️ See warning below about Shadow DOM and selector strings.
##### fallbackFocus
`typescript`
HTMLElement | SVGElement | string | () => HTMLElement | SVGElement | string
By default, an error will be thrown if the focus trap contains no elements in its tab order. With this option you can specify a fallback element to programmatically receive focus if no other tabbable elements are found. For example, you may want a popover's
to receive focus if the popover's content includes no tabbable elements. Make sure the fallback element has a negative tabindex so it can be programmatically focused. The option value can be a DOM node, a selector string (which will be passed to document.querySelector() to find the DOM node), or a function that returns any of these.- If
initialFocus is false (or a function that returns false), this function will not be called when the trap is activated, and no element will be initially focused. This function may still be called while the trap is active if things change such that there are no longer any tabbable nodes in the trap.
- ⚠️ See warning below about Shadow DOM and selector strings.##### escapeDeactivates
`typescript
boolean | (e: KeyboardEvent) => boolean
`Default:
. If false or returns false, the Escape key will not trigger deactivation of the focus trap. This can be useful if you want to force the user to make a decision instead of allowing an easy way out. Note that if a function is given, it's only called if the ESC key was pressed.##### clickOutsideDeactivates
`typescript
boolean | (e: MouseEvent | TouchEvent) => boolean
`If
or returns true, a click outside the focus trap will immediately deactivate the focus trap and allow the click event to do its thing (i.e. to pass-through to the element that was clicked). This option takes precedence over allowOutsideClick when it's set to true. Default: false.- If a function is provided, it will be called up to twice (but only if the click occurs outside the trap's containers): First on the
mousedown (or touchstart on mobile) event and, if true was returned, again on the click event. It will get the same node each time, and it's recommended that the returned value is also the same each time. Be sure to check the event type if the double call is an issue in your code.
- ⚠️ If you're using a password manager such as 1Password, where the app adds a clickable icon to all fillable fields, you should avoid using this option, and instead use the allowOutsideClick option to better control exactly when the focus trap can be deactivated. The clickable icons are usually positioned absolutely, floating on top of the fields, and therefore not part of the container the trap is managing. When using the clickOutsideDeactivates option, clicking on a field's 1Password icon will likely cause the trap to be unintentionally deactivated.##### allowOutsideClick
`typescript
boolean | (e: MouseEvent | TouchEvent) => boolean
`If set and is or returns
, a click outside the focus trap will not be prevented (letting focus temporarily escape the trap, without deactivating it), even if clickOutsideDeactivates=false. Default: false.- If this is a function, it will be called up to twice on every click (but only if the click occurs outside the trap's containers): First on
mousedown (or touchstart on mobile), and then on the actual click if the function returned true on the first event. Be sure to check the event type if the double call is an issue in your code.
- 💡 When clickOutsideDeactivates=true, this option is ignored (i.e. if it's a function, it will not be called).
- Use this option to control if (and even which) clicks are allowed outside the trap in conjunction with clickOutsideDeactivates=false.##### returnFocusOnDeactivate
`typescript
boolean
`Default:
. If false, when the trap is deactivated, focus will not return to the element that had focus before activation.- 💬 When using this option in conjunction with
clickOutsideDeactivates=true:
- If returnFocusOnDeactivate=true and the outside click causing deactivation is on a focusable element, focus will __not__ return to that element; instead, it will return to the node focused just before activation.
- If returnFocusOnDeactivate=false and the outside click is on a focusable node, focus will __remain__ on that node instead of the node focused just before activation. If the outside click is on a non-focusable node, then "nothing" will have focus post-deactivation.##### setReturnFocus
`typescript
HTMLElement | SVGElement | string | (previousActiveElement: HTMLElement | SVGElement) => HTMLElement | SVGElement | string | false
`By default, on deactivation, if
(or if returnFocus=true in the deactivation options), focus will be returned to the element that was focused just before activation. With this option, you can specify another element to programmatically receive focus after deactivation. It can be a DOM node, a selector string (which will be passed to document.querySelector() to find the DOM node upon deactivation), or a function that returns any of these to call upon deactivation (i.e. the selector and function options are only executed at the time the trap is deactivated). Can also be false (or return false) to leave focus where it is at the time of deactivation.- 💬 Using the selector or function options is a good way to return focus to a DOM node that may not exist at the time the trap is activated.
- ⚠️ See warning below about Shadow DOM and selector strings.
##### preventScroll
`typescript
boolean
`By default, focus() will scroll to the element if not in viewport. It can produce unintended effects like scrolling back to the top of a modal. If set to
, no scroll will happen.##### delayInitialFocus
`typescript
boolean
`Default:
. Delays the autofocus to the next execution frame when the focus trap is activated. This prevents elements within the focusable element from capturing the event that triggered the focus trap activation.🔺 Note that when this option is
true (default), it means the initial element to be focused will not be focused until after onPostActivate or onPostUnpause are called.##### isolateSubtrees
`typescript
boolean | 'inert' | 'aria-hidden'
`Default:
. Isolates the portion of the DOM tree containing the focus trap when activated. This prevents screen readers and other assistive technologies from accessing page content outside of the trap. "aria-hidden" will utilize the aria-hidden attribute. true, "inert", and all other truthy values will use the inert attribute. When the trap is deactivated, any elements that were inert or aria-hidden prior to activation will be left in their original state.🔺 Note that when this option uses
inert, all user interactions outside of the trapped element are prevented and content will be inaccessible to screen readers. This prevents the use of the clickOutsideDeactivates feature.🔺 Note that when this option is used and the trap is activated, elements that are siblings to either the trap's container or any of its ancestor elements have
inert or aria-hidden applied. If any of these elements is already inert or aria-hidden, the trap will not remove the attribute from that element when deactivating the trap. Manual changes to these attributes while a trap is active is likely to cause headaches.##### document
`typescript
Document
`Default:
. Document where the focus trap will be active. This enables the use of FocusTrap inside an iFrame.- ⚠️ Note that FocusTrap will be unable to trap focus outside the iFrame if you configure this option to be the iFrame's document. It will only trap focus _inside_ of it (as the demo shows). If you want to trap focus _outside_ as well, then your FocusTrap must be configured on an element that contains the iFrame.
##### tabbableOptions
Tabbable options configurable on FocusTrap (all the common options).
- ⚠️ See notes about testing in JSDom (e.g. using Jest).
##### trapStack
`typescript
Array
`Define the global trap stack. This makes it possible to share the same stack in multiple instances of
in the same page such that auto-activation/pausing of traps is properly coordinated among all instances as activating a trap when another is already active should result in the other being auto-paused. By default, each instance will have its own internal stack, leading to conflicts if they each try to trap the focus at the same time.##### isKeyForward
`typescript
(event: KeyboardEvent) => boolean
`Determines if the given keyboard event is a "tab forward" event that will move the focus to the next trapped element in tab order. Defaults to the
key. Use this to override the trap's behavior if you want to use arrow keys to control keyboard navigation within the trap, for example. Also see isKeyBackward() option.- ⚠️ Using this option will not automatically prevent use of the
TAB key as the browser will continue to respond to it by moving focus forward because that's what using the TAB key does in a browser, but it will no longer respect the trap's container edges as it normally would. You will need to add your own keydown handler to call preventDefault() on a TAB key event if you want to completely suppress the use of the TAB key.##### isKeyBackward
`typescript
(event: KeyboardEvent) => boolean
`Determines if the given keyboard event is a "tab backward" event that will move the focus to the previous trapped element in tab order. Defaults to the
key. Use this to override the trap's behavior if you want to use arrow keys to control keyboard navigation within the trap, for example. Also see isKeyForward() option.- ⚠️ Using this option will not automatically prevent use of the
SHIFT+TAB key as the browser will continue to respond to it by moving focus backward because that's what using the SHIFT+TAB key sequence does in a browser, but it will no longer respect the trap's container edges as it normally would. You will need to add your own keydown handler to call preventDefault() on a TAB key event if you want to completely suppress the use of the SHIFT+TAB key sequence.#### Shadow DOM
##### Selector strings
⚠️ Beware that putting a focus-trap inside an open Shadow DOM means you must not use selector strings for options that support these (because nodes inside Shadow DOMs, even open shadows, are not visible via
document.querySelector()).##### Closed shadows
If you have closed shadow roots that you would like considered for tabbable/focusable nodes, use the
tabbableOptions.getShadowRoot option to provide Tabbable (used internally) with a reference to a given node's shadow root so that it can be searched for candidates.#### Positive Tabindexes
⚠️ Using positive tab indexes (i.e.
) is not recommended, primarily for accessibility reasons. Supporting them properly also means a lot of hoops to jump through when Shadow DOM is used as some key DOM APIs like Node.compareDocumentPosition() do not properly support Shadow DOM.As such, focus-trap considers using positive tabindexes an edge case and only supports them in __single-container__ traps with some caveats for related edge case behavior (see the demo for more details).
If you try to create a multi-container trap where at least one container has one node with a positive tabindex, an exception will be thrown:
`
At least one node with a positive tabindex was found in one of your focus-trap's multiple containers. Positive tabindexes are only supported in single-container focus-traps.
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typescript
trap.active: boolean
`True if the trap is currently active.
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typescript
trap.paused: boolean
`True if the trap is currently paused.
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typescript
trap.activate([activateOptions]) => FocusTrap
`Activates the focus trap, adding various event listeners to the document.
If focus is already within it the trap, it remains unaffected. Otherwise, focus-trap will try to focus the following nodes, in order:
-
- The first tabbable node in the trap
- If none of the above exist, an error will be thrown. You cannot have a focus trap that lacks focus.
Returns the
.activateOptions:These options are used to override the focus trap's default behavior for this particular activation.
- onActivate
{() => void}: Default: whatever you chose for createOptions.onActivate. null or false are the equivalent of a noop.
- onPostActivate {() => void}: Default: whatever you chose for createOptions.onPostActivate. null or false are the equivalent of a noop.
- checkCanFocusTrap {(containers: Array: Default: whatever you chose for createOptions.checkCanFocusTrap.$3
`typescript
trap.deactivate([deactivateOptions]) => FocusTrap
`Deactivates the focus trap.
Returns the
.deactivateOptions:These options are used to override the focus trap's default behavior for this particular deactivation.
- returnFocus
{boolean}: Default: whatever you set for createOptions.returnFocusOnDeactivate. If true, then the setReturnFocus option (specified when the trap was created) is used to determine where focus will be returned.
- onDeactivate {() => void}: Default: whatever you set for createOptions.onDeactivate. null or false are the equivalent of a noop.
- onPostDeactivate {() => void}: Default: whatever you set for createOptions.onPostDeactivate. null or false are the equivalent of a noop.
- checkCanReturnFocus {(trigger: HTMLElement | SVGElement) => Promise: Default: whatever you set for createOptions.checkCanReturnFocus. Not called if the returnFocus option is falsy. trigger is either the originally focused node prior to activation, or the result of the setReturnFocus configuration option.$3
`typescript
trap.pause([pauseOptions]) => FocusTrap
`Pause an active focus trap's event listening without deactivating the trap.
If the focus trap has not been activated, nothing happens.
Whether the trap is already paused or not, its paused state becomes __manually-paused__ even if the trap has already been auto-paused as a result of another trap being activated after this one (and so being higher on the stack than this one).
> Note that a manually-paused trap will not be auto-unpaused if it becomes the trap at the top of the
again by way of all other traps higher than it on the stack being deactivated. It will remain paused until manually unpaused by calling unpause(). If the trap was auto-paused the entire time it was not at the top of the stack, then it will be auto-unpaused when it gets to the top of the stack again.Returns the
trap.Any
onDeactivate callback will not be called, and focus will not return to the element that was focused before the trap's activation. But the trap's behavior will be paused.This is useful in various cases, one of which is when you want one focus trap within another.
demo-six exemplifies how you can implement this.pauseOptions:These options are used to override the focus trap's default behavior for this particular pausing.
- onPause
{() => void}: Default: whatever you chose for createOptions.onPause. null or false are the equivalent of a noop.
- onPostPause {() => void}: Default: whatever you chose for createOptions.onPostPause. null or false are the equivalent of a noop.$3
`typescript
trap.unpause([unpauseOptions]) => FocusTrap
`Unpause an active focus trap. (See
, above.)Focus is forced into the trap just as described for
focusTrap.activate().If the focus trap has not been activated, nothing happens.
If the focus trap has not been paused, nothing happens other than resetting its __manually-paused__ state.
If the focus trap is not at the top of the
trapStack, it will not be unpaused (whether previously auto- or manually-paused) until all traps higher on the stack have been deactivated and this trap becomes the one at the top again.Returns the
trap.unpauseOptions:These options are used to override the focus trap's default behavior for this particular unpausing.
- onUnpause
{() => void}: Default: whatever you chose for createOptions.onUnpause. null or false are the equivalent of a noop.
- onPostUnpause {() => void}: Default: whatever you chose for createOptions.onPostUnpause. null or false are the equivalent of a noop.$3
`typescript
trap.updateContainerElements(HTMLElement | SVGElement | string | Array) => FocusTrap
`Update the element(s) that are used as containers for the focus trap.
When you call
, you give it an element (or selector), or an array of elements (or selectors) to keep the focus within. This method simply allows you to update which elements to keep the focus within even while the trap is active.A use case for this is found in focus-trap-react, where React
ref's may not be initialized yet, but when they are you want to have them be a container element.Returns the
trap.Examples
Read code in
docs/ and see how it works.Here's generally what happens in
default.js (the "default behavior" demo):`js
const { createFocusTrap } = require('../../index');const container = document.getElementById('default');
const focusTrap = createFocusTrap('#default', {
onActivate: () => container.classList.add('is-active'),
onDeactivate: () => container.classList.remove('is-active'),
});
document
.getElementById('activate-default')
.addEventListener('click', focusTrap.activate);
document
.getElementById('deactivate-default')
.addEventListener('click', focusTrap.deactivate);
`Other details
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Only one focus trap can be listening at a time. If a second focus trap is activated the first will automatically pause. The first trap is unpaused and again traps focus when the second is deactivated.
Focus trap manages a queue of traps: if A activates; then B activates, pausing A; then C activates, pausing B; when C then deactivates, B is unpaused; and when B then deactivates, A is unpaused.
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The focus trap will work best if the first and last focusable elements in your trap are simple elements that all browsers treat the same, like buttons and inputs.**
Tabbing will work as expected with trickier, less predictable elements — like iframes, shadow trees, audio and video elements, etc. — as long as they are between more predictable elements (that is, if they are not the first or last tabbable element in the trap).
This limitation is ultimately rooted in browser inconsistencies and inadequacies, but it comes to focus-trap through its dependency Tabbable. You can read about more details in the Tabbable documentation.
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You can't have a focus trap without focus, so an error will be thrown if you try to initialize focus-trap with an element that contains no tabbable nodes.
If you find yourself in this situation, you should give you container
and set it as initialFocus or fallbackFocus. A couple of demos illustrate this.Development
Because of the nature of the functionality, involving keyboard and click and (especially) focus events, JavaScript unit tests don't make sense. After all, JSDom does not fully support focus events. Since the demo was developed to also be the test, we use Cypress to automate running through all demos in the demo page.
Help
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> ⚠️ JSDom is not officially supported. Your mileage may vary, and tests may break from one release to the next (even a patch or minor release).
>
> This topic is just here to help with what we know may affect your tests.
In general, a focus trap is best tested in a full browser environment such as Cypress, Playwright, or Nightwatch where a full DOM is available.
Sometimes, that's not entirely desirable, and depending on what you're testing, you may be able to get away with using JSDom (e.g. via Jest), but you'll have to configure your traps using the
tabbableOptions.displayCheck: 'none' option.See Testing tabbable in JSDom for more details.
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This error happens when the containers you specified when you setup your focus trap do not have -- or no longer have -- any tabbable elements in them, which means that focus will inevitably escape your trap because focus __must__ always go _somewhere_.
You will hit this error if your trap does not have (or no longer has) any tabbable (and therefore focusable) elements in it, and it was not configured with a backup element (see the
fallbackFocus option -- which must still be in the trap, but does not necessarily have to be tabbable, i.e. it could have tabindex="-1", making it focusable, but not tabbable).This often happens when traps are related to elements that appear and disappear dynamically. Typically, the error will fire either as the element is being shown (because the trap gets created before the trapped children have been inserted into the DOM), or as it's being hidden (because the trapped children are destroyed before the trap is either destroyed or disabled).
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If you create a trap and try to use the TAB key to set focus to the first element in your trap, the first element seems unreachable because focus keeps skipping over it for some reason.
This can happen in projects where the Angular-related zone.js module is being used because Zone can interfere with Focus-trap's ability to control where focus goes when it _leaves an edge node_ (that is, a node that is on the edge of a container in which it is trapping focus).
What is actually happening is that Focus-trap is correctly wrapping focus around to that first element (or last element, if going in reverse with SHIFT+TAB, and you're seeing that get skipped) and setting focus to it, but because of Zone's interference (in which Focus-trap's call to
preventDefault()` on the focus event triggered by the TAB key press is rendered ineffective), once Focus-trap is done handling the event, the browser hasn't received the signal that its default behavior should be prevented, and so it proceeds to move focus to the _next_ element -- effectively "skipping" over the element to which Focus-trap set focus, making it seem "unreachable".Unfortunately, there's no good workaround to this issue from Focus-trap's perspective. The issue was reported to Angular (not by Focus-trap) and has a PR (also not by Focus-trap) for a fix.
This was originally investigated in #1165 if you want to go deeper.
Contributing
See CONTRIBUTING.
Contributors
In alphabetical order:
