client.batch is not a function

[jurrienk]

When updating from v3->v4 I can no longer use the batch() function on the redisClient object.

The migration guide makes no reference of this being unsupported.

setting legacyMode to true does not resolve this.

Environment:

• Node.js Version: v14" -->
• Node Redis Version: 4.0.1

[leibale]

We definitely need to add it to the migration guide and changelog (I'll leave this issue open until we'll do it), but:

1. As described here, commands from the same "event loop tick" are "batched" anyway.
2. In case you use .batch as a way to queue commands and execute them later, you can do:

const [getReply, setReply] = await client.multi()
  .get('1')
  .set('2', '2')
  .execAsPipeline();

// you can "save" a "multi" instance and use it later
const multi = client.multi();
process.on('message', message => {
  if (message === 'EXEC') {
    return multi.execAsPipeline();
  }

  multi.sAdd('messages', message);
});