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| 1 | +import type {ParseSelector} from 'typed-query-selector/parser.d.js'; |
| 2 | + |
| 3 | +export type DelegateOptions = boolean | AddEventListenerOptions; |
| 4 | +export type EventType = keyof GlobalEventHandlersEventMap; |
| 5 | + |
| 6 | +export type DelegateEventHandler< |
| 7 | + TEvent extends Event = Event, |
| 8 | + TElement extends Element = Element, |
| 9 | +> = (event: DelegateEvent<TEvent, TElement>) => void; |
| 10 | + |
| 11 | +export type DelegateEvent< |
| 12 | + TEvent extends Event = Event, |
| 13 | + TElement extends Element = Element, |
| 14 | +> = TEvent & { |
| 15 | + delegateTarget: TElement; |
| 16 | +}; |
| 17 | + |
| 18 | +export function castAddEventListenerOptions( |
| 19 | + options: DelegateOptions | undefined, |
| 20 | +): AddEventListenerOptions { |
| 21 | + return typeof options === 'object' ? options : {capture: options}; |
| 22 | +} |
| 23 | + |
| 24 | +/** Keeps track of raw listeners added to the base elements to avoid duplication */ |
| 25 | +const ledger = new WeakMap< |
| 26 | +EventTarget, |
| 27 | +WeakMap<DelegateEventHandler, Set<string>> |
| 28 | +>(); |
| 29 | + |
| 30 | +function editLedger( |
| 31 | + wanted: boolean, |
| 32 | + baseElement: EventTarget | Document, |
| 33 | + callback: DelegateEventHandler<any, any>, |
| 34 | + setup: string, |
| 35 | +): boolean { |
| 36 | + if (!wanted && !ledger.has(baseElement)) { |
| 37 | + return false; |
| 38 | + } |
| 39 | + |
| 40 | + const elementMap |
| 41 | + = ledger.get(baseElement) |
| 42 | + ?? new WeakMap<DelegateEventHandler, Set<string>>(); |
| 43 | + ledger.set(baseElement, elementMap); |
| 44 | + |
| 45 | + const setups = elementMap.get(callback) ?? new Set<string>(); |
| 46 | + elementMap.set(callback, setups); |
| 47 | + |
| 48 | + const existed = setups.has(setup); |
| 49 | + if (wanted) { |
| 50 | + setups.add(setup); |
| 51 | + } else { |
| 52 | + setups.delete(setup); |
| 53 | + } |
| 54 | + |
| 55 | + return existed && wanted; |
| 56 | +} |
| 57 | + |
| 58 | +function isEventTarget( |
| 59 | + elements: EventTarget | Document | Iterable<Element> | string, |
| 60 | +): elements is EventTarget { |
| 61 | + return typeof (elements as EventTarget).addEventListener === 'function'; |
| 62 | +} |
| 63 | + |
| 64 | +function safeClosest(event: Event, selector: string): Element | void { |
| 65 | + let target = event.target; |
| 66 | + if (target instanceof Text) { |
| 67 | + target = target.parentElement; |
| 68 | + } |
| 69 | + |
| 70 | + if (target instanceof Element && event.currentTarget instanceof Element) { |
| 71 | + // `.closest()` may match ancestors of `currentTarget` but we only need its children |
| 72 | + const closest = target.closest(selector); |
| 73 | + if (closest && event.currentTarget.contains(closest)) { |
| 74 | + return closest; |
| 75 | + } |
| 76 | + } |
| 77 | +} |
| 78 | + |
| 79 | +/** |
| 80 | + * Delegates event to a selector. |
| 81 | + * @param options A boolean value setting options.capture or an options object of type AddEventListenerOptions |
| 82 | + */ |
| 83 | +function delegate< |
| 84 | + Selector extends string, |
| 85 | + TElement extends Element = ParseSelector<Selector, HTMLElement>, |
| 86 | + TEventType extends EventType = EventType, |
| 87 | +>( |
| 88 | + base: EventTarget | Document | Iterable<Element> | string, |
| 89 | + selector: Selector, |
| 90 | + type: TEventType, |
| 91 | + callback: DelegateEventHandler<GlobalEventHandlersEventMap[TEventType], TElement>, |
| 92 | + options?: DelegateOptions |
| 93 | +): void; |
| 94 | + |
| 95 | +function delegate< |
| 96 | + TElement extends Element = HTMLElement, |
| 97 | + TEventType extends EventType = EventType, |
| 98 | +>( |
| 99 | + base: EventTarget | Document | Iterable<Element> | string, |
| 100 | + selector: string, |
| 101 | + type: TEventType, |
| 102 | + callback: DelegateEventHandler<GlobalEventHandlersEventMap[TEventType], TElement>, |
| 103 | + options?: DelegateOptions |
| 104 | +): void; |
| 105 | + |
| 106 | +// This type isn't exported as a declaration, so it needs to be duplicated above |
| 107 | +function delegate< |
| 108 | + TElement extends Element, |
| 109 | + TEventType extends EventType = EventType, |
| 110 | +>( |
| 111 | + base: EventTarget | Document | Iterable<Element> | string, |
| 112 | + selector: string, |
| 113 | + type: TEventType, |
| 114 | + callback: DelegateEventHandler<GlobalEventHandlersEventMap[TEventType], TElement>, |
| 115 | + options?: DelegateOptions, |
| 116 | +): void { |
| 117 | + const listenerOptions = castAddEventListenerOptions(options); |
| 118 | + |
| 119 | + const {signal} = listenerOptions; |
| 120 | + |
| 121 | + if (signal?.aborted) { |
| 122 | + return; |
| 123 | + } |
| 124 | + |
| 125 | + // Handle Selector-based usage |
| 126 | + if (typeof base === 'string') { |
| 127 | + base = document.querySelectorAll(base); |
| 128 | + } |
| 129 | + |
| 130 | + // Handle Array-like based usage |
| 131 | + if (!isEventTarget(base)) { |
| 132 | + for (const element of base) { |
| 133 | + delegate(element, selector, type, callback, listenerOptions); |
| 134 | + } |
| 135 | + |
| 136 | + return; |
| 137 | + } |
| 138 | + |
| 139 | + // Don't pass `once` to `addEventListener` because it needs to be handled in `delegate-it` |
| 140 | + const {once, ...nativeListenerOptions} = listenerOptions; |
| 141 | + |
| 142 | + // `document` should never be the base, it's just an easy way to define "global event listeners" |
| 143 | + const baseElement = base instanceof Document ? base.documentElement : base; |
| 144 | + |
| 145 | + // Handle the regular Element usage |
| 146 | + const capture = Boolean(typeof options === 'object' ? options.capture : options); |
| 147 | + const listenerFn = (event: Event): void => { |
| 148 | + const delegateTarget = safeClosest(event, selector); |
| 149 | + if (delegateTarget) { |
| 150 | + const delegateEvent = Object.assign(event, {delegateTarget}); |
| 151 | + callback.call(baseElement, delegateEvent as DelegateEvent<GlobalEventHandlersEventMap[TEventType], TElement>); |
| 152 | + if (once) { |
| 153 | + baseElement.removeEventListener(type, listenerFn, nativeListenerOptions); |
| 154 | + editLedger(false, baseElement, callback, setup); |
| 155 | + } |
| 156 | + } |
| 157 | + }; |
| 158 | + |
| 159 | + const setup = JSON.stringify({selector, type, capture}); |
| 160 | + const isAlreadyListening = editLedger(true, baseElement, callback, setup); |
| 161 | + if (!isAlreadyListening) { |
| 162 | + baseElement.addEventListener(type, listenerFn, nativeListenerOptions); |
| 163 | + } |
| 164 | + |
| 165 | + signal?.addEventListener('abort', () => { |
| 166 | + editLedger(false, baseElement, callback, setup); |
| 167 | + }); |
| 168 | +} |
| 169 | + |
| 170 | +export default delegate; |
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