NuxtJS comes with some default polyfills, and it is recommended not to use the same ones from polyfill.io. Doing this would increase the page weight unnecessarily, affecting the page-loading performance.

Polyfills for IE11 compatibility are added by default. Along with this, polyfills for the following are also added by default:

• fetch() replaces whatwg-fetch and unfetch on the client-side, and isomorphic-unfetch and node-fetch on the server-side.
• URL of NodeJS is supported through URL.
• object-assign, object.assign, and core-js/object/assign are supported by Object.assign()
• Supports all ES6 features out of the box

• NextJS also supports many features beyond ES6:

  • Async/await (ES2017)
  • Object rest/spread properties (ES2018)
  • Dynamic import() (ES2020)
  • Optional chaining (ES2020)
  • Nullish coalescing (ES2020)
  • Class fields and static properties (part of stage 3 proposal)
• Built in Typescript support.

Bad Practice

import { Head } from "next/document";
export class Card extends Head {
  render() {
    const data = Object.assign(source, target)
    return (
      <div>
        <h1>Hello title</h1>
        <script src="https://polyfill.io/v3/polyfill.min.js?features=Object.assign"></script>
      </div>
    );
  }
}

Recommended

import { Head } from "next/document";
export class Card extends Head {
  render() {
    const data = Object.assign(source, target)
    return (
      <div>
        <h1>Hello title</h1>
      </div>
    );
  }
}

References

• Nextjs Supported Browsers and Features