client.js

  listThenGetMessages() {
    const getMessageListCommandName = '#0';
    
    const body = new BodyBuilder()
      .appendGetMessageList({}, getMessageListCommandName)
      .appendGetMessages({
        "#ids": {
          "resultOf": getMessageListCommandName,
          "name": "getMessageList",
          "path": "/messageIds"
        }
      }, '#1')
      .getBody();

    return this._jmapRequestWithMultipleCommands(body);
  }