dom-observe/dist/DOM/DOMObserver.js

 ![node](https://img.shields.io/node/v/dom-observ

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.DOMObserver = void 0;
const events_1 = require("events");
const delay_me_1 = require("delay-me");
class DOMObserver {
    /**
     * @param {SelectorCallback<T>} selector
     * @param {IDOMObserverInitParameters<T>>} parameters
     */
    constructor(selector, parameters) {
        this.emitter = new events_1.EventEmitter();
        this.observer = null;
        this._is_active = false;
        this._parameters = null;
        this._state = 'disappeared';
        this.$elementRef = null;
        this._parameters = parameters;
        this.selector = selector;
        this.observeProcess = this.observeProcess.bind(this);
        this.onMutationOccurred = this.onMutationOccurred.bind(this);
    }
    get isActive() { return this._is_active; }
    get parameters() { return Object.assign({}, this._parameters); }
    /**
     * Starts DOM observation
     */
    start() {
        if (this._is_active)
            return;
        this._is_active = true;
        this.emit('start');
        delay_me_1.setImmediate(this.observeProcess);
    }
    /**
     * Stops DOM observation
     */
    stop() {
        if (!this._is_active)
            return;
        this._is_active = false;
        this.observer.disconnect();
        this.observer = null;
        this.emit('stop');
    }
    /**
     * @returns {Promise<void>}
     * @protected
     */
    async observeProcess() {
        if (!this._is_active)
            return;
        switch (this._state) {
            case 'appeared':
                {
                    if (this.$elementRef === null || !document.contains(this.$elementRef)) {
                        this._state = 'disappeared';
                        if (this.observer !== null) {
                            this.observer.disconnect();
                            this.observer = null;
                        }
                        const $element = this.$elementRef;
                        this.$elementRef = null;
                        this.emit('disappear', $element);
                    }
                }
                break;
            case 'disappeared':
                {
                    let $element = this.selector.apply(null, []);
                    if ($element !== null) {
                        this._state = 'appeared';
                        this.$elementRef = $element;
                        this.emit('appear', $element);
                        if (this.observer !== null) {
                            this.observer.disconnect();
                            this.observer = null;
                        }
                        if (!this._is_active)
                            return;
                        this.observer = new MutationObserver(this.onMutationOccurred);
                        this.observer.observe(this.$elementRef, this._parameters);
                    }
                }
                break;
        }
        if (this._is_active) {
            await delay_me_1.sleep(this.parameters.interval);
            delay_me_1.setImmediate(this.observeProcess);
        }
    }
    /**
     * @param {MutationRecord[]} mutations
     * @protected
     */
    onMutationOccurred(mutations) {
        if (!this._is_active)
            return;
        this.emit('change', this.$elementRef, mutations);
    }
    emit(event, ...args) {
        this.emitter.emit(event, ...args);
    }
    on(event, listener) {
        this.emitter.on(event, listener);
        return this;
    }
    once(event, listener) {
        this.emitter.once(event, listener);
        return this;
    }
    off(event, listener) {
        this.emitter.off(event, listener);
        return this;
    }
}
exports.DOMObserver = DOMObserver;