swiper/core/update/updateActiveIndex.js

Most modern mobile touch slider and framework with hardware accelerated transitions

export function getActiveIndexByTranslate(swiper) {
  const {
    slidesGrid,
    params
  } = swiper;
  const translate = swiper.rtlTranslate ? swiper.translate : -swiper.translate;
  let activeIndex;
  for (let i = 0; i < slidesGrid.length; i += 1) {
    if (typeof slidesGrid[i + 1] !== 'undefined') {
      if (translate >= slidesGrid[i] && translate < slidesGrid[i + 1] - (slidesGrid[i + 1] - slidesGrid[i]) / 2) {
        activeIndex = i;
      } else if (translate >= slidesGrid[i] && translate < slidesGrid[i + 1]) {
        activeIndex = i + 1;
      }
    } else if (translate >= slidesGrid[i]) {
      activeIndex = i;
    }
  }
  // Normalize slideIndex
  if (params.normalizeSlideIndex) {
    if (activeIndex < 0 || typeof activeIndex === 'undefined') activeIndex = 0;
  }
  return activeIndex;
}
export default function updateActiveIndex(newActiveIndex) {
  const swiper = this;
  const translate = swiper.rtlTranslate ? swiper.translate : -swiper.translate;
  const {
    snapGrid,
    params,
    activeIndex: previousIndex,
    realIndex: previousRealIndex,
    snapIndex: previousSnapIndex
  } = swiper;
  let activeIndex = newActiveIndex;
  let snapIndex;
  const getVirtualRealIndex = aIndex => {
    let realIndex = aIndex - swiper.virtual.slidesBefore;
    if (realIndex < 0) {
      realIndex = swiper.virtual.slides.length + realIndex;
    }
    if (realIndex >= swiper.virtual.slides.length) {
      realIndex -= swiper.virtual.slides.length;
    }
    return realIndex;
  };
  if (typeof activeIndex === 'undefined') {
    activeIndex = getActiveIndexByTranslate(swiper);
  }
  if (snapGrid.indexOf(translate) >= 0) {
    snapIndex = snapGrid.indexOf(translate);
  } else {
    const skip = Math.min(params.slidesPerGroupSkip, activeIndex);
    snapIndex = skip + Math.floor((activeIndex - skip) / params.slidesPerGroup);
  }
  if (snapIndex >= snapGrid.length) snapIndex = snapGrid.length - 1;
  if (activeIndex === previousIndex) {
    if (snapIndex !== previousSnapIndex) {
      swiper.snapIndex = snapIndex;
      swiper.emit('snapIndexChange');
    }
    if (swiper.params.loop && swiper.virtual && swiper.params.virtual.enabled) {
      swiper.realIndex = getVirtualRealIndex(activeIndex);
    }
    return;
  }
  // Get real index
  let realIndex;
  if (swiper.virtual && params.virtual.enabled && params.loop) {
    realIndex = getVirtualRealIndex(activeIndex);
  } else if (swiper.slides[activeIndex]) {
    realIndex = parseInt(swiper.slides[activeIndex].getAttribute('data-swiper-slide-index') || activeIndex, 10);
  } else {
    realIndex = activeIndex;
  }
  Object.assign(swiper, {
    snapIndex,
    realIndex,
    previousIndex,
    activeIndex
  });
  swiper.emit('activeIndexChange');
  swiper.emit('snapIndexChange');
  if (previousRealIndex !== realIndex) {
    swiper.emit('realIndexChange');
  }
  if (swiper.initialized || swiper.params.runCallbacksOnInit) {
    swiper.emit('slideChange');
  }
}