Webpack production build error Assignment to constant variable. when mouse dragging

[wise1999]

Hi,
I'm using Sage 9 Wordpress Theme for Development that uses Webpack. When I'm in dev mode everything works fine, but in production it throws an error while mouse dragging a slider. It no longer slides to another slide, but it acts like "freemode".

Uncaught TypeError: Assignment to constant variable. at C. Piece of code with this:

            function C(o) {
                if (s(S, jn, A),
                s(S, Bn, C),
                b) {
                    if (E || o.cancelable && I()) {
                        const i = function(n) {
                            if (t.is(kn) || !k) {
                                const t = v === b && w || v
                                  , e = M(b) - M(t)
                                  , o = z(n) - z(t)
                                  , i = z(n) - z(b) < Dn;
                                if (o && i)
                                    return e / o
                            }
                            return 0
                        }(o)
                          , r = (i = i, <= here it throws an error
                        g() + rt(i) * V(et(i) * (e.flickPower || 600), $ ? 1 / 0 : n.Layout.listSize() * (e.flickMaxPages || 1)));
                        $ ? a.scroll(r) : t.is(Pn) ? a.go(t.index + p(rt(i))) : a.go(a.toDest(r), !0),
                        H(o)
                    }
                    i(kt)
                }
                var r;
                E = !1
            }

It breaks with same error on every subpage on my site where it uses splide.

Example of code with splide:

import Splide from '@splidejs/splide';

export default {
  init() {
    $(function () {
      var splidesCount = document.querySelectorAll('.section-main .splide')

      for (var i = 0; i < splidesCount.length; i++) {
        new Splide(splidesCount[i], {
          perPage: 4,
          perMove: 1,
          type: 'loop',
          arrows: true,
          pagination: true,
          gap: '2.8rem',
          padding: '1rem',
          autoplay: true,
          breakpoints: {
            1300: {
              gap: '2rem',
              perPage: 3,
            },
            992: {
              padding: '1.5rem',
              perPage: 2,
            },
            768: {
              padding: '1rem',
              perPage: 1,
            },
          },
        }).mount();
      }
    });
  },
};

Tbh don't know if its a problem with splide itself, or with webpack or event with uglifyjs from bundle. :/

[wise1999]

Okay, so I solved this by removing compress options and changing ecma from 5 to 8 in UglifyJsPlugin.

webpack.config.optimize.js file:

    new UglifyJsPlugin({
      uglifyOptions: {
        ecma: 8,
      },
    }),

[NaotoshiFujita]

The plugin has been already deprecated 😐
https://github.com/webpack-contrib/uglifyjs-webpack-plugin