This JavaScript code uses the Webex SDK to perform three sequential actions chained together with promises.

1. First, webex.rooms.create() is called to create a new Webex space named 'Q3 Budget Planning'.
2. The promise then resolves, passing the new room object as x. webex.memberships.create() is called to add a person to that room, using x.id to specify the roomId.
3. Finally, after the membership is created, webex.messages.create() is called to post a message into the same room. The roomId for this action is retrieved from the membership object y created in the previous step.

Webex JS SDK - Rooms: The official SDK documentation shows that webex.rooms.create({title: '...'}) is the correct method for creating a new space.

Source: Webex for Developers, SDK API Documentation

URL: https://webex.github.io/webex-js-sdk/api/#webexroomscreate

Webex JS SDK - Memberships: The documentation confirms that webex.memberships.create({roomId: '...', personEmail: '...'}) is used to add a user to a room.

Source: Webex for Developers, SDK API Documentation

URL: https://webex.github.io/webex-js-sdk/api/#webexmembershipscreate

Webex JS SDK - Messages: The webex.messages.create({roomId: '...', text: '...'}) method is documented as the standard way to post a message to a room.

Source: Webex for Developers, SDK API Documentation

URL: https://webex.github.io/webex-js-sdk/api/#webexmessagescreate