PolymerElement class constructor cannot be called without a "new"

Question

My application worked fine yesterday, but now when I do polymer serve -o, it opens the application and prints this error in the console.

Class constructor PolymerElement cannot be invoked without 'new'

Answer 1

• Delete cached files and images from the browser cache.
• If you downloaded custom-elements-es5-adapter.js, delete it.
• Then use $ polymer serve -compile never.

According to this post , this problem is the reason because $ polymer is used to compile your code on es5 automatically. The -compile option never stops the execution of $ polymer because of this.

Answer 2

Polymer v.2.
:

, custom-elements-es5-adapter.js .

, ES6, ES5. ES5- ES5 ES6, HTMLElement.

Answer 3

Polymer es5- Android- WebView. .

Answer 4

polymer.json custom-elements-es5-adapter excludes, ES5.

  "builds": [
    {
      "bundle": {
        "stripComments": true,
        "inlineCss": true,
        "sourcemaps": false,
        "excludes": [
          "bower_components/webcomponentsjs/webcomponents-loader.js",
          "bower_components/webcomponentsjs/custom-elements-es5-adapter.js"
        ]
      },
      "js": {
        "compile": true,
        "minify": true
      },
      "css": {
        "minify": true
      },
      "html": {
        "minify": true
      },
      "addServiceWorker": false

Answer 5

, , Parcel. , Custom Elements v1 ES6. Parcel ES5 - , Typescript tsconfig ES6.

, Parcel, , , ES5. - "browserlist" package.json.

I found out about this through this video . For more information, I suggest you look at this.