Js Reflow: [Violation] Forced reflow while executing JavaScript took ~200ms

[0m3r]

popular place swiper.js line 506
line 506 took 75 % of time

  function css(props, value) {
    var i;
    if (arguments.length === 1) {
      if (typeof props === 'string') {
        if (this[0]) { return win.getComputedStyle(this[0], null).getPropertyValue(props); } //line 506 took 75 % of time
      } else {

[0m3r]

one more possible improvment

      setTimeout(() => {

      $images.each(function (imageIndex, imageEl) {
        var $imageEl = $(imageEl);
        $imageEl.addClass(params.loadingClass);

[0m3r]

related
nolimits4web/swiper#2465

[0m3r]

possible improvement

split init function

Utils.nextTick(() => {
swiper.updateSize();

Swiper.prototype.init = function init() {
            var swiper = this;
            if (swiper.initialized) {
                return;
            }
            swiper.emit('beforeInit');
            if (swiper.params.breakpoints) {
                swiper.setBreakpoint();
            }
            swiper.addClasses();
            if (swiper.params.loop) {
                swiper.loopCreate();
            }
            Utils.nextTick(() => {
                swiper.updateSize();
                swiper.updateSlides();
                if (swiper.params.watchOverflow) {
                    swiper.checkOverflow();
                }
                if (swiper.params.grabCursor) {
                    swiper.setGrabCursor();
                }
                if (swiper.params.preloadImages) {
                    swiper.preloadImages();
                }
                if (swiper.params.loop) {
                    swiper.slideTo(swiper.params.initialSlide + swiper.loopedSlides, 0, swiper.params.runCallbacksOnInit);
                } else {
                    swiper.slideTo(swiper.params.initialSlide, 0, swiper.params.runCallbacksOnInit);
                }
                swiper.attachEvents();
                swiper.initialized = true;
                swiper.emit('init');
            });
        }
        
        ```