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node-creation-observer

Callback binding for HTML Node creation events

Fra og med 21.05.2016. Se den nyeste version.

Dette script bør ikke installeres direkte. Det er et bibliotek, som andre scripts kan inkludere med metadirektivet // @require https://updategreasyfork.deno.dev/scripts/19857/126895/node-creation-observer.js 

/**
 * https://github.com/soufianesakhi/node-creation-observer-js
 * MIT licensed
 * Copyright (c) 2016 Soufiane Sakhi
 */

var NodeCreationObserver = function () {
    var mutationObserver = null;
    var observedNodeAttribute = "node-creation-observer";
    var listeners = {};
    var options = {
        childList: true,
        subtree: true
    };

    function ListenerContext(removeOnFirstMatch) {
        this.callbacks = [];
        this.removeOnFirstMatch = removeOnFirstMatch == undefined ? false : removeOnFirstMatch;
    }

    function onMutationCallback(mutationRecordArray) {
        Object.keys(listeners).forEach(function (selector) {
            invokeCallbacks(selector);
        });
    }

    function invokeCallbacks(selector) {
        var callbacks = listeners[selector].callbacks;
        var elements = document.querySelectorAll(selector);
        var newElements = filterNewElements(elements);
        if (newElements.length > 0) {
            if (listeners[selector].removeOnFirstMatch) {
                removeListener(selector);
            }
            newElements.forEach(function (element) {
                callbacks.forEach(function (callback) {
                    callback.call(element, element);
                });
            });
        }
    }

    function filterNewElements(elements) {
        var newElements = [];
        for (var i = 0; i < elements.length; i++) {
            var element = elements[i];
            var attr = element.getAttribute(observedNodeAttribute);
            if (attr == null) {
                element.setAttribute(observedNodeAttribute, 1);
                newElements.push(element);
            }
        };
        return newElements;
    }

    function observe() {
        if (mutationObserver == null) {
            mutationObserver = new MutationObserver(onMutationCallback);
            mutationObserver.observe(document.documentElement, options);
        }
    }

    function removeListener(selector) {
        delete listeners[selector];
        if (Object.keys(listeners).length == 0) {
            stopObserving();
        }
    }

    function stopObserving() {
        if (mutationObserver != null) {
            mutationObserver.disconnect();
            mutationObserver = null;
        }
    }

    return {
        onCreation: function (selector, callback, removeOnFirstMatch) {
            if (!listeners[selector]) {
                listeners[selector] = new ListenerContext(removeOnFirstMatch);
            }
            listeners[selector].callbacks.push(callback);
            observe();
            if (document.querySelector(selector) != null) {
                invokeCallbacks(selector);
            }
        },
        remove: removeListener,
        stop: function () {
            listeners = {};
            stopObserving();
        }
    };
} ();