ex-helpers-element/src/watch.ts

import {ElementRef} from '@angular/core';
import extend from 'lodash-es/extend';
import {IncrementalStackManager} from '@ex-helpers/stack';
import {bounds} from './bounds';
import './element';

interface SizeCollectionItem {
    triggerCheck: () => void;
    startCountdown: () => void;
    callback: (height: number, width: number) => void;
    observer?: MutationObserver;
    id?: number;
    legacy?: boolean;
}

const DEFAULT_OPTIONS = {
    attributes: true,
    childList: true,
    characterData: true
};

ElementRef.prototype.watchSize = function
(callback: (height: number, width: number) => void,
 options?: { attributes?: boolean, childList?: boolean, characterData?: boolean },
 params: { timeout?: number, legacy: boolean } = {legacy: false}) {
    if (!this._watchSizeCollection) {
        Object.defineProperty(this, '_watchSizeCollection', {
            enumerable: false,
            configurable: true,
            writable: false,
            value: new IncrementalStackManager<SizeCollectionItem>('id')
        });
    }
    options = extend(DEFAULT_OPTIONS, options);
    let timeout: any;
    let lastHeight: number;
    let lastWidth: number;
    const triggerCheck = () => {
        const sizes = bounds(this.nativeElement).size;
        if (lastWidth === sizes.width && lastHeight === sizes.height) {
            return;
        }
        lastHeight = sizes.height;
        lastWidth = sizes.width;
        callback(sizes.height, sizes.width);
    };
    const startCountdown = () => {
        clearTimeout(timeout);
        timeout = setTimeout(() => {
            triggerCheck();
        }, params.timeout || 100);
    };
    const item = this._watchSizeCollection.add({
        callback,
        startCountdown,
        triggerCheck
    });
    if (MutationObserver && params.legacy === false) {
        const observer = new MutationObserver(mutations => {
            startCountdown();
        });
        item.observer = observer;
        item.legacy = false;
        startCountdown();
        observer.observe(this.nativeElement, options);
        return () => observer.disconnect();
    } else {
        item.legacy = true;
        const checkInterval = setInterval(() => {
            triggerCheck();
        }, 200);
        startCountdown();
        return () => clearInterval(checkInterval);
    }
};

ElementRef.prototype.triggerSizeCheck = function () {
    if (this._watchSizeCollection) {
        this._watchSizeCollection.execute('triggerCheck');
    }
};

ElementRef.prototype.watchChanges = function (callback: MutationCallback, options: MutationObserverInit) {
    if (MutationObserver) {
        const observer = new MutationObserver(callback);
        observer.observe(this.nativeElement, options);
        return () => observer.disconnect();
    }
    return () => {
    };
};