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Failed to construct 'HTMLElement': Please use the 'new' operator #5

playground opened this Issue Jul 4, 2018 · 2 comments


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playground commented Jul 4, 2018

the example works, but when I try to apply that to my component, it keeps throwing these errors on

customElements.define('custom-element', customElement);

Uncaught TypeError: Failed to construct 'HTMLElement': Please use the 'new' operator, this DOM object constructor cannot be called as a function.
    at NgElementImpl.NgElement [as constructor] (elements.js:391)
    at new NgElementImpl (elements.js:427)
    at new AppModule (app.module.ts:42)
    at createClass (core.js:8213)
    at createProviderInstance$1 (core.js:8185)
    at initNgModule (core.js:8118)
    at new NgModuleRef
    at createNgModuleRef (core.js:8833)
    at Object.debugCreateNgModuleRef [as createNgModuleRef] (core.js:10658)
    at NgModuleFactory
.push.../../node_modules/@angular/core/fesm5/core.js.NgModuleFactory_.create (core.js:11360)


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manfredsteyer commented Jul 6, 2018

Does this happen in the example app or in your own?

This error means, that you need a polyfill for browser that do support (!) Custom Elements. That sounds a bit strange, but Custom Elements are defined for EcmaScript 2015+ (bases upon classes) and for supporting older browser, we normally compile down to EcmaScript 5 today.

Normally, I'm loading this polyfill:

npm i @webcomponents/custom-elements --save

And then, I'm referencing it in the angular.json:

"scripts": [

To support browsers that DO NOT know Custom Elements, I'm also referencing another polyfill of this package in the polyfills.ts:

import '@webcomponents/custom-elements/custom-elements.min';

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DanielNetzer commented Nov 18, 2018

Following your instructions i'm still having the same error.
when I bundle following your instructions I get 2 files, is there anyway to bundle them into a single file as well?

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