import { applyPolyfill, ReflowStrategy, rerenderInnerHTML } from 'custom-elements-hmr-polyfill'; // apply polly fill rerenderInnerHTML(); // if you want to customize... applyPolyfill( /* no reflowing */ ReflowStrategy.NONE, /* ignored, because reflowing is disabled */ -1, /* gets called for every re-definition of a web component */ (elementName: string) => { console.log(elementName, 'updated'); } );