Crash in legacy browsers on new Headers(undefined)

[IlyaSemenov]

Environment

ofetch 1.4.1
Chrome 49

Reproduction

Describe the bug

Similarly to the problem that was originally resolved in #235, the library now crashes here in legacy browsers:

ofetch/src/utils.ts

Line 116 in c817be8

return new Headers(input);

due to new Headers(undefined) not being supported in runtime.

The code could be easily updated in a similar fashion, but I'm not sure if it should be? In my project, I decided to add a polyfill wrapper class around Headers instead of patching ofetch. Maybe we should actually revert #235 and document the workaround?

Additional context

Polyfill

// Legacy browsers crash on new Headers(undefined)
// See https://github.com/unjs/ofetch/pull/235

try {
  // eslint-disable-next-line no-new
  new Headers(undefined)
} catch (
  // eslint-disable-next-line unused-imports/no-unused-vars
  _err
) {
  // eslint-disable-next-line no-global-assign
  Headers = (function (Base) {
    return class Headers extends Base {
      constructor(init) {
        super(init || {})
      }
    }
  })(Headers)
}

Logs

[kricsleo]

Not sure if we should still polyfill this for legacy users in 2025, according to the FAQ

Why not transpiled?

By transpiling libraries, we push the web backward with legacy code which is unneeded for most of the users.

If you need to support legacy users, you can optionally transpile the library in your build pipeline.

If we need to handle this finally, it would be better to patch (or extend) the Header constructor to prevent this issue from happening again.

ofetch/src/index.ts

Line 31 in c817be8

export const Headers = _globalThis.Headers;