2018-05-28 15:09:11 +02:00
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import { SCROLLING_SPEED } from '../constants';
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2017-08-29 13:56:54 +02:00
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export default class List {
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element: HTMLElement;
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scrollPos: number;
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height: number;
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constructor({ element }: { element: HTMLElement }) {
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this.element = element;
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this.scrollPos = this.element.scrollTop;
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this.height = this.element.offsetHeight;
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}
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clear(): void {
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this.element.innerHTML = '';
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}
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append(node: Element | DocumentFragment): void {
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this.element.appendChild(node);
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}
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getChild(selector: string): HTMLElement | null {
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return this.element.querySelector(selector);
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}
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hasChildren(): boolean {
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return this.element.hasChildNodes();
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}
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scrollToTop(): void {
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this.element.scrollTop = 0;
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}
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scrollToChildElement(element: HTMLElement, direction: 1 | -1): void {
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if (!element) {
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return;
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}
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const listHeight = this.element.offsetHeight;
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// Scroll position of dropdown
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const listScrollPosition = this.element.scrollTop + listHeight;
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const elementHeight = element.offsetHeight;
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// Distance from bottom of element to top of parent
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const elementPos = element.offsetTop + elementHeight;
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// Difference between the element and scroll position
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const destination =
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direction > 0
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? this.element.scrollTop + elementPos - listScrollPosition
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: element.offsetTop;
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requestAnimationFrame(() => {
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this._animateScroll(destination, direction);
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});
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}
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_scrollDown(scrollPos: number, strength: number, destination: number): void {
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const easing = (destination - scrollPos) / strength;
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const distance = easing > 1 ? easing : 1;
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this.element.scrollTop = scrollPos + distance;
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}
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_scrollUp(scrollPos: number, strength: number, destination: number): void {
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const easing = (scrollPos - destination) / strength;
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const distance = easing > 1 ? easing : 1;
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this.element.scrollTop = scrollPos - distance;
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}
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_animateScroll(destination: number, direction: number): void {
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const strength = SCROLLING_SPEED;
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const choiceListScrollTop = this.element.scrollTop;
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let continueAnimation = false;
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if (direction > 0) {
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this._scrollDown(choiceListScrollTop, strength, destination);
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if (choiceListScrollTop < destination) {
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continueAnimation = true;
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}
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} else {
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this._scrollUp(choiceListScrollTop, strength, destination);
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if (choiceListScrollTop > destination) {
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continueAnimation = true;
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}
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}
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if (continueAnimation) {
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requestAnimationFrame(() => {
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this._animateScroll(destination, direction);
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});
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}
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}
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}
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