react-native-ui-lib/src/components/carousel/CarouselPresenter.js

<p align="center"> <img src="https://user-images.githubusercontent.com/1780255/105469025-56759000-5ca0-11eb-993d-3568c1fd54f4.png" height="250px" style="display:block"/> </p> <p align="center">UI Toolset & Components Library for React Native</p> <p a

import React from 'react';
import _ from 'lodash';
export function getChildrenLength(props) {
  return React.Children.count(props.children);
}
export function calcOffset(props, state) {
  const {
    currentPage,
    pageWidth,
    pageHeight
  } = state;
  const {
    loop,
    containerMarginHorizontal = 0
  } = props;
  const actualCurrentPage = loop ? currentPage + 1 : currentPage;
  const nonLoopAdjustment = !loop && currentPage > 0 ? containerMarginHorizontal : 0;
  const pageSize = props.horizontal ? pageWidth : pageHeight;
  const offset = pageSize * actualCurrentPage - nonLoopAdjustment;
  const offsetXY = {
    x: props.horizontal ? offset : 0,
    y: props.horizontal ? 0 : offset
  };
  return offsetXY;
}
export function calcPageIndex(offset, props, pageSize) {
  const pagesCount = getChildrenLength(props);
  const {
    loop
  } = props;
  const pageIndexIncludingClonedPages = Math.round(offset / pageSize);
  let actualPageIndex;

  if (loop) {
    actualPageIndex = (pageIndexIncludingClonedPages + (pagesCount - 1)) % pagesCount;
  } else {
    actualPageIndex = Math.min(pagesCount - 1, pageIndexIncludingClonedPages);
  }

  return actualPageIndex;
}
export function isOutOfBounds(offset, props, pageWidth) {
  const length = getChildrenLength(props);
  const minLimit = 1;
  const maxLimit = (length + 1) * pageWidth - 1;
  return !_.inRange(offset, minLimit, maxLimit);
}