|
| 1 | +/** |
| 2 | + * List of focusable elements within the trap |
| 3 | + */ |
| 4 | +let focusableElements |
| 5 | +/** |
| 6 | + * First element in the focus sequence |
| 7 | + */ |
| 8 | +let firstFocusableElement |
| 9 | +/** |
| 10 | + * Last element in the focus sequence |
| 11 | + */ |
| 12 | +let lastFocusableElement |
| 13 | +/** |
| 14 | + * CSS selector for focusable elements |
| 15 | + */ |
| 16 | +let focusableElementsSelector |
| 17 | + |
| 18 | +let focusableElementsContainer |
| 19 | + |
| 20 | +/** |
| 21 | + * Resets list of focusable elements and manages trap destruction |
| 22 | + * @returns {void} |
| 23 | + */ |
| 24 | +const resetFocusableElements = () => { |
| 25 | + focusableElements = Array.from( |
| 26 | + (focusableElementsContainer || document).querySelectorAll( |
| 27 | + focusableElementsSelector |
| 28 | + ) |
| 29 | + ).filter((element) => { |
| 30 | + return ( |
| 31 | + (element.offsetWidth > 0 || element.offsetHeight > 0) && |
| 32 | + element.disabled !== true |
| 33 | + ) |
| 34 | + }) |
| 35 | + firstFocusableElement = focusableElements[0] |
| 36 | + lastFocusableElement = focusableElements.at(-1) |
| 37 | + |
| 38 | + if (!firstFocusableElement || !lastFocusableElement) { |
| 39 | + destroyFocusTrap() |
| 40 | + } |
| 41 | +} |
| 42 | + |
| 43 | +/** |
| 44 | + * Initializes focusable elements and creates temporary anchor element |
| 45 | + * Creates invisible button to capture initial focus and handle boundary cases |
| 46 | + * @returns {void} |
| 47 | + */ |
| 48 | +const initFocusableElements = () => { |
| 49 | + resetFocusableElements() |
| 50 | + |
| 51 | + if (firstFocusableElement) { |
| 52 | + const temporaryFirstFocusableElement = document.createElement('button') |
| 53 | + temporaryFirstFocusableElement.setAttribute( |
| 54 | + 'style', |
| 55 | + 'position: absolute; top: -100px;' |
| 56 | + ) |
| 57 | + |
| 58 | + firstFocusableElement.before(temporaryFirstFocusableElement) |
| 59 | + |
| 60 | + temporaryFirstFocusableElement.addEventListener('blur', () => { |
| 61 | + temporaryFirstFocusableElement.remove() |
| 62 | + resetFocusableElements() |
| 63 | + }) |
| 64 | + |
| 65 | + firstFocusableElement = temporaryFirstFocusableElement |
| 66 | + |
| 67 | + temporaryFirstFocusableElement.focus() |
| 68 | + } |
| 69 | +} |
| 70 | + |
| 71 | +/** |
| 72 | + * Handles keyboard navigation constraints |
| 73 | + * @param {KeyboardEvent} event - Keyboard event |
| 74 | + * @returns {void} |
| 75 | + */ |
| 76 | +const handleKeyDown = (event) => { |
| 77 | + resetFocusableElements() |
| 78 | + if (!document.body.contains(firstFocusableElement)) { |
| 79 | + destroyFocusTrap() |
| 80 | + return |
| 81 | + } |
| 82 | + |
| 83 | + if (event.key === 'Tab') { |
| 84 | + if (!firstFocusableElement || !lastFocusableElement) { |
| 85 | + destroyFocusTrap() |
| 86 | + return |
| 87 | + } |
| 88 | + |
| 89 | + // After click adress bar or developer tool, the document.activeElement will be empty, so we need to init it again |
| 90 | + if (!focusableElements.includes(document.activeElement)) { |
| 91 | + initFocusableElements() |
| 92 | + } |
| 93 | + |
| 94 | + if (event.shiftKey) { |
| 95 | + if (document.activeElement === firstFocusableElement) { |
| 96 | + lastFocusableElement.focus() |
| 97 | + event.preventDefault() |
| 98 | + } |
| 99 | + } else if (document.activeElement === lastFocusableElement) { |
| 100 | + firstFocusableElement.focus() |
| 101 | + event.preventDefault() |
| 102 | + } |
| 103 | + } |
| 104 | +} |
| 105 | + |
| 106 | +/** |
| 107 | + * Destroys focus trap by removing event listeners |
| 108 | + * @returns {void} |
| 109 | + */ |
| 110 | +function destroyFocusTrap() { |
| 111 | + document.removeEventListener('keydown', handleKeyDown) |
| 112 | +} |
| 113 | + |
| 114 | +/** |
| 115 | + * Initializes focus trap with custom container and selector |
| 116 | + * @param {Object} [container] - Container element to scope the focus trap |
| 117 | + * @param {string} [selector] - CSS selector for focusable elements (optional) |
| 118 | + * @returns {void} |
| 119 | + * |
| 120 | + * @description When called with single parameter: |
| 121 | + * - Default selector: 'a, button, input, textarea, select, details, [tabindex]:not([tabindex="-1"])' |
| 122 | + */ |
| 123 | +export function initFocusTrap(container, selector) { |
| 124 | + focusableElementsContainer = container |
| 125 | + focusableElementsSelector = |
| 126 | + selector || |
| 127 | + 'a, button, input, textarea, select, details, [tabindex]:not([tabindex="-1"])' |
| 128 | + document.addEventListener('keydown', handleKeyDown) |
| 129 | + initFocusableElements() |
| 130 | +} |
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