Move size functions to utils

src/utils/size.js

@@ -0,0 +1,33 @@
+export function getPagesCount({ slidesCount, perPage }) {
+  return Math.ceil(slidesCount/perPage)
+}
+
+export function getPerPageTail({
+  perPage,
+  slidesCount,
+  pagesCount
+}) {
+  return slidesCount - perPage * (pagesCount - 1)
+}
+
+export function getIsNotCompletePage({
+  pageIndex,
+  pagesCount,
+}) {
+  return pageIndex === pagesCount - 1 && pagesCount !== 1
+}
+
+export function getSlideSize({
+  contentContainerWidth,
+  perPage,
+  perPageTail,
+  isNotCompletePage
+}) {
+  return isNotCompletePage
+    ? Math.round(contentContainerWidth/perPageTail) 
+    : Math.round(contentContainerWidth/perPage)
+}
+
+export function getPageIndex({ slideIndex, perPage }) {
+  return Math.floor(slideIndex/perPage)
+}