web-ui-pack/helpers/onFocusGot.js

Web package with UI elements

import onFocusLost from "./onFocusLost";
export default function onFocusGot(element, listener, options) {
    let isLost = true;
    let removeLost;
    const remove = () => {
        removeLost?.call(element);
        element.removeEventListener("focusin", focusin);
    };
    const focusin = (e) => {
        if (!isLost) {
            return;
        }
        const isFocused = (a) => element === a || element.contains(a);
        const isPrevFocused = e.relatedTarget instanceof Node && isFocused(e.relatedTarget);
        removeLost = removeLost || onFocusLost(element, () => (isLost = true), options);
        if (!isPrevFocused) {
            listener.call(element, e);
            options?.once && remove();
            isLost = false;
        }
    };
    element.addEventListener("focusin", focusin, { passive: true, ...options });
    return remove;
}