focustrap.js
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/**
* --------------------------------------------------------------------------
* Bootstrap util/focustrap.js
* Licensed under MIT (https://github.com/twbs/bootstrap/blob/main/LICENSE)
* --------------------------------------------------------------------------
*/
import EventHandler from '../dom/event-handler.js'
import SelectorEngine from '../dom/selector-engine.js'
import Config from './config.js'
/**
* Constants
*/
const NAME = 'focustrap'
const DATA_KEY = 'bs.focustrap'
const EVENT_KEY = `.${DATA_KEY}`
const EVENT_FOCUSIN = `focusin${EVENT_KEY}`
const EVENT_KEYDOWN_TAB = `keydown.tab${EVENT_KEY}`
const TAB_KEY = 'Tab'
const TAB_NAV_FORWARD = 'forward'
const TAB_NAV_BACKWARD = 'backward'
const Default = {
autofocus: true,
trapElement: null // The element to trap focus inside of
}
const DefaultType = {
autofocus: 'boolean',
trapElement: 'element'
}
/**
* Class definition
*/
class FocusTrap extends Config {
constructor(config) {
super()
this._config = this._getConfig(config)
this._isActive = false
this._lastTabNavDirection = null
}
// Getters
static get Default() {
return Default
}
static get DefaultType() {
return DefaultType
}
static get NAME() {
return NAME
}
// Public
activate() {
if (this._isActive) {
return
}
if (this._config.autofocus) {
this._config.trapElement.focus()
}
EventHandler.off(document, EVENT_KEY) // guard against infinite focus loop
EventHandler.on(document, EVENT_FOCUSIN, event => this._handleFocusin(event))
EventHandler.on(document, EVENT_KEYDOWN_TAB, event => this._handleKeydown(event))
this._isActive = true
}
deactivate() {
if (!this._isActive) {
return
}
this._isActive = false
EventHandler.off(document, EVENT_KEY)
}
// Private
_handleFocusin(event) {
const { trapElement } = this._config
if (event.target === document || event.target === trapElement || trapElement.contains(event.target)) {
return
}
const elements = SelectorEngine.focusableChildren(trapElement)
if (elements.length === 0) {
trapElement.focus()
} else if (this._lastTabNavDirection === TAB_NAV_BACKWARD) {
elements[elements.length - 1].focus()
} else {
elements[0].focus()
}
}
_handleKeydown(event) {
if (event.key !== TAB_KEY) {
return
}
this._lastTabNavDirection = event.shiftKey ? TAB_NAV_BACKWARD : TAB_NAV_FORWARD
}
}
export default FocusTrap