react-hooks-global-scrollspy/lib/scrollSpy/useScrollSpy.js

React Hook for managing navigation by scroll position

var __assign = (this && this.__assign) || function () {
    __assign = Object.assign || function(t) {
        for (var s, i = 1, n = arguments.length; i < n; i++) {
            s = arguments[i];
            for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p))
                t[p] = s[p];
        }
        return t;
    };
    return __assign.apply(this, arguments);
};
import { useEffect, useState, useRef, useCallback } from "react";
import { throttle } from "../utils/throttle";
/**
 * @param ScrollSpyParams Optional params
 * @param ScrollSpyParams.offsetPx Distance from Y coordinate of the base (px)
 * @param ScrollSpyParams.throttleMs Interval of update processing (ms)
 * @returns [ activeElement, actions ] - Two return values are returned as an array
 * @returns activeElement - DOM element activated based on scroll position (only one)
 * @returns actions - Actions are used to control registered DOM elements
 */
export var useScrollSpy = function (_a) {
    var _b = _a === void 0 ? {} : _a, _c = _b.offsetPx, offsetPx = _c === void 0 ? 0 : _c, _d = _b.throttleMs, throttleMs = _d === void 0 ? 50 : _d;
    var _e = useState(null), activeElement = _e[0], setActiveElement = _e[1];
    var elements = useRef({});
    var registerElement = useCallback(function (_a) {
        var _b;
        var key = _a.key, element = _a.element;
        var prevElements = elements.current;
        elements.current = __assign(__assign({}, prevElements), (_b = {}, _b[key] = element, _b));
    }, []);
    var unregisterElement = useCallback(function (_a) {
        var key = _a.key;
        var deletedElements = __assign({}, elements.current);
        delete deletedElements[key];
        elements.current = deletedElements;
    }, []);
    var resetElements = useCallback(function () {
        elements.current = {};
    }, []);
    var updateActiveElement = useCallback(function () {
        var currentElements = elements.current;
        var elementKeys = Object.keys(currentElements);
        var activeKey = elementKeys.reduce(function (prevActive, key) {
            var elementElement = currentElements[key].current;
            if (!elementElement) {
                return prevActive;
            }
            var elementPositionTop = elementElement.getBoundingClientRect().top;
            var isPassed = elementPositionTop + offsetPx < 0;
            if (!isPassed) {
                return prevActive;
            }
            if (!prevActive.key) {
                return {
                    key: key,
                    elementPositionTop: elementPositionTop,
                };
            }
            var _a = prevActive.elementPositionTop, prevElementPositionTop = _a === void 0 ? 0 : _a;
            var isHigherThanPrev = elementPositionTop >= prevElementPositionTop;
            if (isHigherThanPrev) {
                return {
                    key: key,
                    elementPositionTop: elementPositionTop,
                };
            }
            else {
                return prevActive;
            }
        }, {}).key;
        if (!activeKey) {
            setActiveElement(null);
            return;
        }
        setActiveElement({
            key: activeKey,
            value: currentElements[activeKey],
        });
    }, [offsetPx]);
    useEffect(function () {
        var InvokeUpdate = throttle(updateActiveElement, throttleMs);
        window.addEventListener("scroll", InvokeUpdate);
        return function () {
            window.removeEventListener("scroll", InvokeUpdate);
        };
    }, [throttleMs, updateActiveElement]);
    var actions = {
        registerElement: registerElement,
        unregisterElement: unregisterElement,
        resetElements: resetElements,
    };
    return [activeElement, actions];
};