swiper/core/update/updateSlidesProgress.js

import $ from '../../shared/dom.js';
export default function updateSlidesProgress(translate = this && this.translate || 0) {
  const swiper = this;
  const params = swiper.params;
  const {
    slides,
    rtlTranslate: rtl,
    snapGrid
  } = swiper;
  if (slides.length === 0) return;
  if (typeof slides[0].swiperSlideOffset === 'undefined') swiper.updateSlidesOffset();
  let offsetCenter = -translate;
  if (rtl) offsetCenter = translate; // Visible Slides

  slides.removeClass(params.slideVisibleClass);
  swiper.visibleSlidesIndexes = [];
  swiper.visibleSlides = [];

  for (let i = 0; i < slides.length; i += 1) {
    const slide = slides[i];
    let slideOffset = slide.swiperSlideOffset;

    if (params.cssMode && params.centeredSlides) {
      slideOffset -= slides[0].swiperSlideOffset;
    }

    const slideProgress = (offsetCenter + (params.centeredSlides ? swiper.minTranslate() : 0) - slideOffset) / (slide.swiperSlideSize + params.spaceBetween);
    const originalSlideProgress = (offsetCenter - snapGrid[0] + (params.centeredSlides ? swiper.minTranslate() : 0) - slideOffset) / (slide.swiperSlideSize + params.spaceBetween);
    const slideBefore = -(offsetCenter - slideOffset);
    const slideAfter = slideBefore + swiper.slidesSizesGrid[i];
    const isVisible = slideBefore >= 0 && slideBefore < swiper.size - 1 || slideAfter > 1 && slideAfter <= swiper.size || slideBefore <= 0 && slideAfter >= swiper.size;

    if (isVisible) {
      swiper.visibleSlides.push(slide);
      swiper.visibleSlidesIndexes.push(i);
      slides.eq(i).addClass(params.slideVisibleClass);
    }

    slide.progress = rtl ? -slideProgress : slideProgress;
    slide.originalProgress = rtl ? -originalSlideProgress : originalSlideProgress;
  }

  swiper.visibleSlides = $(swiper.visibleSlides);
}