@mornya/react-image-libs/esm/ImageObserver.js

The project of React.js Image library.

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);
};
export var ImageObserver;
(function (ImageObserver) {
    var Provider = (function () {
        function Provider(option) {
            this.subscribe = this.subscribe.bind(this);
            this.subscribeOnce = this.subscribeOnce.bind(this);
            this.unsubscribe = this.unsubscribe.bind(this);
            this.destroy = this.destroy.bind(this);
            var observerOption = __assign({ root: null, rootMargin: '0px 0px 0px 0px', threshold: 0 }, option);
            this.intersectionObserver = new IntersectionObserver(function (entries, observer) {
                entries.forEach(function (entry) {
                    if (entry.isIntersecting) {
                        observer.unobserve(entry.target);
                        entry.target.dispatchEvent(new CustomEvent('imageObserverIntersecting', {
                            detail: __assign(__assign({}, entry), { unsubscribe: function () {
                                    observer.unobserve(entry.target);
                                } }),
                        }));
                    }
                });
            }, observerOption);
        }
        Provider.prototype.subscribe = function (target, subscribeCallback) {
            var callbackHandler = function (event) {
                return subscribeCallback(event);
            };
            target.addEventListener('imageObserverIntersecting', callbackHandler, false);
            this.intersectionObserver.observe(target);
            return function () {
                target.removeEventListener('imageObserverIntersecting', callbackHandler);
            };
        };
        Provider.prototype.subscribeOnce = function (target, subscribeCallback) {
            var _this = this;
            var callbackHandler = function (event) {
                _this.unsubscribe(target);
                return subscribeCallback(event);
            };
            target.addEventListener('imageObserverIntersecting', callbackHandler, { once: true, capture: false });
            this.intersectionObserver.observe(target);
        };
        Provider.prototype.unsubscribe = function (target) {
            this.intersectionObserver.unobserve(target);
        };
        Provider.prototype.destroy = function () {
            var _this = this;
            this.intersectionObserver.takeRecords().forEach(function (entry) { return _this.intersectionObserver.unobserve(entry.target); });
            this.intersectionObserver.disconnect();
        };
        return Provider;
    }());
    ImageObserver.Provider = Provider;
})(ImageObserver || (ImageObserver = {}));