Handing DISCO#info requests

The one last bit that we want to complete is the handleIq() function that we alluded to in the handleMessage() function. This function will respond with a message giving the capabilities offered by this server-side component specifically, its ability to play XMPPong, which is indicated in part by the identity of the reply as well as the feature that contains the XMPPong namespace:

const handleIq = (stanza) => {
    const query = stanza.getChild('query',
       'http://jabber.org/protocol/disco#info')
    if (!query) return
    const reply = new Stanza(
      'iq',
      {
        type: 'result',
    id: stanza.attrs.id,
    from: stanza.attrs.to,
    to: stanza.attrs.from
      }
    )
     .c('query', { xmlns: 'http://jabber.org/protocol/disco#info' })
     reply.c('identity',{category: 'chat', name: 'XMPPong', type:'text'})
     reply.c('feature', { var: PONG_NAMESPACE })
    ...