loader fail with Unexpected token

[Well]

./node_modules/.pnpm/uint8array-extras@0.5.0/node_modules/uint8array-extras/index.js 34:15
Module parse failed: Unexpected token (34:15)
File was processed with these loaders:

• ./node_modules/.pnpm/babel-loader@8.0.6_@babel+core@7.7.4_webpack@4.41.2/node_modules/babel-loader/lib/index.js
  You may need an additional loader to handle the result of these loaders.
  | }
  |

totalLength ??= arrays.reduce((accumulator, currentValue) => accumulator + currentValue.length, 0);
| const returnValue = new Uint8Array(totalLength);
| let offset = 0;

[Sindre Sorhus]

This is a problem with your bundler, not this package.