You can always access basic identifying information for the current viewer.

Users of your extension have the option to share their Twitch identity with you.
MEDKit lets an administrator request a list of all users who are currently sharing this information.

This list is not exposed to users with viewer or broadcaster role. It is available only to users with the admin role for the extension.

Get Current Viewer Information

Use the JavaScript SDK.user object to access information on the current viewer.
The user object has these properties:

For example:

const medkit = new Muxy.SDK();
await medkit.loaded();

console.log(`Viewer ${  sdk.user.twitchID ? 'has' : 'has not' } shared their Twitch ID with the extension`);
console.log(`They are currently ${sdk.user.buffer}ms behind the stream.`);

Get Twitch IDs of Extension Users

To request the current list of shared Twitch IDs, call sdk.getExtensionUsers(). The functionality is only available to broadcasters who have the admin role, and (in production) only on Muxy's "admin" pages. You cannot make the call from Twitch's Creator Dashboard.

For example:

const opts = new Muxy.DebuggingOptions();
opts.role('admin');
Muxy.debug(opts);

const medkit = new Muxy.SDK();
medkit.loaded().then(() => {
  medkit.getExtensionUsers().then((resp) => {
    resp.results.forEach((u) => {
      console.log(u.twitch_id);
    });

    console.log(`There are ${resp.next === '0' ? 'no ' : ''}more results available`);
  });
});

The JSON response from this method has the following structure:

{
  next: '0',
  results: [
    { twitch_id: '12345' },
    { twitch_id: '23456' },
    { twitch_id: '34567' }
  ]
}

Iterating for large numbers of users

The getExtensionUsers() call returns at most 1,000 objects in its response. If more than 1,000 users have shared their identity with your extension, you have to make more calls to iterate through 1000-user pages. Each page is indexed, and the getExtensionUsers() method takes an optional page index parameter.

The following example demonstrates the basic method for iterating through current users. The next field in the response to each call contains the 0-based page index for the next page, or the value "0" if all
results have been returned. Pass the next value directly to getExtensionUsers() to get the next page of up to 1,000 users. Use a next value of 0 to begin the iteration.

const opts = new Muxy.DebuggingOptions();
opts.role('admin');
Muxy.debug(opts);

const medkit = new Muxy.SDK();
medkit.loaded().then(() => {
  function getNextUsers(cursor) {
    medkit.getExtensionUsers(cursor).then((resp) => {
      resp.results.forEach((u) => {
        console.log(u.twitch_id);
      });

      if (resp.next !== '0') {
       // this example does not limit the number of responses
        getNextUsers(resp.next);
      }
    });
  }

  getNextUsers('0');
});

🚧

Be careful!

For very successful extensions, you can easily overload your connection if you do not further limit the number of calls.
If a million users have shared their ID with your extension, this code will very quickly make 1,000 API requests.