Failed to construct 'HTMLElement'

Question

I run my-widget.js through babel (es2015 preset) to produce my-widget-es5.js. This causes an error with Polymer.

Class constructor         


        

Answer 1

According to SO user @joncarlson:

You may find a solution by using the custom-elements-es5-adapter.js file proposed as a workaround by Webcomponentsjs.

Answer 2

Take a look at the link below. Just use the es5-bundled preset version and you should be ready to go. It will include conditional loading of the custom-elements-es5-adapter.json that @Supersharp mentioned.

https://www.polymer-project.org/2.0/docs/tools/polymer-json#builds