There’s an NPM package containing this implementation called ‘undici’ that you can install in previous versions of Node; the package.json claims support back to 12.x.
However the fetch implementation itself is documented as unstable and only supports Node 16.x. I believe this is because it is not quite spec compliant yet, so there is latitude for breaking changes that make it more spec compliant.
https://www.npmjs.com/package/undici
However the fetch implementation itself is documented as unstable and only supports Node 16.x. I believe this is because it is not quite spec compliant yet, so there is latitude for breaking changes that make it more spec compliant.