react-scroll-tracker/dist/useScrollTracker.js

A React hook for tracking scroll depth with TypeScript support and SSR compatibility

"use strict";
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);
};
var __spreadArray = (this && this.__spreadArray) || function (to, from, pack) {
    if (pack || arguments.length === 2) for (var i = 0, l = from.length, ar; i < l; i++) {
        if (ar || !(i in from)) {
            if (!ar) ar = Array.prototype.slice.call(from, 0, i);
            ar[i] = from[i];
        }
    }
    return to.concat(ar || Array.prototype.slice.call(from));
};
Object.defineProperty(exports, "__esModule", { value: true });
var react_1 = require("react");
var utils_1 = require("./utils");
var useScrollTracker = function (trackScrollDepths, callback) {
    var _a = (0, react_1.useState)({
        scrollDepths: trackScrollDepths,
        scrollY: 0
    }), state = _a[0], setState = _a[1];
    var scrollDepths = state.scrollDepths, scrollY = state.scrollY;
    (0, react_1.useEffect)(function () {
        if (typeof window === 'undefined' || window.pageYOffset === 0) {
            return;
        }
        setState(function (oldState) { return (__assign(__assign({}, oldState), { scrollY: window.pageYOffset })); });
    }, []);
    (0, react_1.useEffect)(function () {
        if (typeof window === 'undefined') {
            return;
        }
        var endScrollTracker = function () {
            return window.removeEventListener('scroll', handleScroll);
        };
        var handleScroll = function () {
            var scrollPercent = (0, utils_1.getScrollPercent)(document);
            if (!scrollDepths) {
                return setState(function (oldState) { return (__assign(__assign({}, oldState), { scrollY: scrollPercent })); });
            }
            var sortedScrollDepths = __spreadArray([], scrollDepths, true).sort(function (a, b) { return a - b; });
            var reachedDepths = sortedScrollDepths.filter(function (depth) { return scrollPercent >= depth; });
            var remainingDepths = sortedScrollDepths.filter(function (depth) { return scrollPercent < depth; });
            if (reachedDepths.length > 0) {
                if (remainingDepths.length === 0) {
                    endScrollTracker();
                }
                if (callback) {
                    reachedDepths.forEach(function (depth, i) {
                        // Remaining = unreached depths + reached depths not yet processed
                        var stillRemaining = __spreadArray(__spreadArray([], reachedDepths.slice(i + 1), true), remainingDepths, true);
                        callback({
                            scrollY: depth,
                            scrollPercent: scrollPercent,
                            remainingDepths: stillRemaining,
                        });
                    });
                }
                setState({
                    scrollY: reachedDepths[reachedDepths.length - 1],
                    scrollDepths: remainingDepths,
                });
            }
        };
        window.addEventListener('scroll', handleScroll);
        return endScrollTracker;
    }, [scrollDepths, callback]);
    return { scrollY: scrollY };
};
exports.default = useScrollTracker;