react-scroll-tracker/dist/useScrollTracker.js

A React hook to help with scroll tracking events, which supports typescript.

"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 __spreadArrays = (this && this.__spreadArrays) || function () {
    for (var s = 0, i = 0, il = arguments.length; i < il; i++) s += arguments[i].length;
    for (var r = Array(s), k = 0, i = 0; i < il; i++)
        for (var a = arguments[i], j = 0, jl = a.length; j < jl; j++, k++)
            r[k] = a[j];
    return r;
};
Object.defineProperty(exports, "__esModule", { value: true });
var react_1 = require("react");
var useScrollTracker = function (trackScrollDepths, callback) {
    var _a = react_1.useState({
        scrollDepths: trackScrollDepths,
        scrollY: 0
    }), state = _a[0], setState = _a[1];
    var scrollDepths = state.scrollDepths, scrollY = state.scrollY;
    react_1.useEffect(function () {
        if (typeof window === 'undefined' || window.pageYOffset === 0) {
            return;
        }
        setState(function (oldState) { return (__assign(__assign({}, oldState), { scrollY: window.pageYOffset })); });
    }, []);
    react_1.useEffect(function () {
        if (typeof window === 'undefined') {
            return;
        }
        var endScrollTracker = function () {
            return window.removeEventListener('scroll', handleScroll);
        };
        var handleScroll = function () {
            var h = document.documentElement;
            var b = document.body;
            var scrollTop = h.scrollTop || b.scrollTop;
            var scrollHeight = h.scrollHeight || b.scrollHeight;
            var clientHeight = h.clientHeight;
            var scrollPercent = (scrollTop / (scrollHeight - clientHeight)) * 100;
            if (scrollDepths) {
                var nextMinDepth_1 = Math.min.apply(Math, __spreadArrays(scrollDepths, [scrollHeight]));
                if (scrollPercent >= nextMinDepth_1) {
                    var updatedScrollDepths = scrollDepths.filter(function (depth) { return depth !== nextMinDepth_1; });
                    if (updatedScrollDepths.length === 0) {
                        endScrollTracker();
                    }
                    if (callback) {
                        callback({
                            scrollY: nextMinDepth_1,
                            scrollPercent: scrollPercent,
                            remainingDepths: updatedScrollDepths,
                        });
                    }
                    setState({
                        scrollY: nextMinDepth_1,
                        scrollDepths: updatedScrollDepths,
                    });
                }
            }
            else {
                setState(__assign(__assign({}, state), { scrollY: scrollPercent }));
            }
        };
        window.addEventListener('scroll', handleScroll);
        return endScrollTracker;
    }, [scrollDepths, scrollY, state]);
    return { scrollY: scrollY };
};
exports.default = useScrollTracker;