meteor__coursera-meteor-2/client/chat_page.js

Template.chat_page.helpers({
  messages: function () {
    const chat = Chats.findOne({ _id: Session.get("chatId") });
    console.log("messages context", this, chat.messages);
    return chat.messages;
  },

  other_user: function () {
  }
});

Template.chat_page.events({
  // this event fires when the user sends a message on the chat page
  "submit .js-send-chat": function (event) {
    // stop the form from triggering a page reload
    event.preventDefault();
    // see if we can find a chat object in the database
    // to which we'll add the message
    const chat = Chats.findOne({ _id: Session.get("chatId") });
    if (chat) {// ok - we have a chat to use
      let msgs = chat.messages; // pull the messages property
      if (!msgs) {// no messages yet, create a new array
        msgs = [];
      }
      // is a good idea to insert data straight from the form
      // (i.e. the user) into the database?? certainly not.
      // push adds the message to the end of the array
      msgs.push({
        text: event.target.chat.value,
        sender: Meteor.userId()
      });
      // reset the form
      event.target.chat.value = "";
      // put the messages array onto the chat object
      chat.messages = msgs;
      // update the chat object in the database.
      Chats.update(chat._id, chat);
    }
  }
});