The Goal

We are building the following functionality:

See the Pen CanJS 5.0 Chat - Final by Bitovi (@bitovi) on CodePen.

Setup

The easiest way to get started is to Fork the following CodePen by clicking the Edit On CodePen button on the top right:

See the Pen CanJS 5.0 Chat - Start by Bitovi (@bitovi) on CodePen.

The CodePen is configured to load Bootstrap for its styles and socket.io for a socket library. It will be connecting to a RESTful and real-time service layer at https://chat.donejs.com/api/messages.

The CodePen also importing core.mjs, which exports all of CanJS's Core APIs as named exports. The following is how you can import different APIs into your app:

import {DefineMap, Component} from "//unpkg.com/can@5/core.mjs"

Read Setting Up CanJS for instructions on how to set up CanJS in a real app. Check out the DoneJS version of this guide.

Hello World

In this section, we will:

• Show a big “Chat Home” title within a Bootstrap container.
• Make it so when “Chat Home” is clicked, an exclamation mark (“!”) is added to the end of the title.

In your CodePen, update the HTML panel to:

• Use the <chat-app> element we will define in the JS panel.

<chat-app></chat-app>

Update the JavaScript panel to:

• Define an application component (chat-app) by extending can-component. Its definition includes:
  • A tag that is the name of the custom element being defined.
  • A can-stache view that contains the contents of the chat-app element. This view:
    • Inserts a message value within a responsive Bootstrap container using {{expression}}.
    • Listen for click events and call addExcitement with on:event.
  • A can-define/map/map ViewModel definition. This definition includes:
    • A message property that is a string value initialized to "Chat Home".
    • An addExcitement method that adds "!" to the end of the message property.

import { Component } from "//unpkg.com/can@5/core.mjs";

Component.extend({
    tag: "chat-app",
    view: `
        <div class="container">
            <div class="row">
                <div class="col-sm-8 col-sm-offset-2">
                    <h1 class="page-header text-center" on:click="this.addExcitement()">
                        {{ this.message }}
                    </h1>
                </div>
            </div>
        </div>`,
    ViewModel: {
        // Properties
        message: {
            type: "string",
            default: "Chat Home"
        },
        // Methods
        addExcitement(){
            this.message = this.message + "!";
        }
    }
});

When complete, you should see a large “Chat Home” title in the Output panel. Click on it and things will get really exciting!

This step sets up the essential basics of a CanJS application — a can-component custom element with a can-stache view and can-define/map/map ViewModel.

The properties and methods the view uses are defined in the ViewModel type. We defined a message and an addExcitement method.

The templates are a dialect of mustache and handlebars syntax. The mustache syntax allows a very terse writing style for the most common patterns within templates:

• inserting data with {{expression}}
• looping with {{#each(expression)}}
• branching with if or {{#is(expressions)}}

Key take-away: You define ViewModel method and property behaviors. The ViewModel methods can be called by can-stache views. The ViewModel properties can be observed by can-stache views.

Route between two pages

In this section we will:

• Create a home page and chat messages page that the user can navigate between with links and the browser’s back and forward button.

Update the JavaScript panel to:

• Update the chat-app component's view to:
  • Check if the ViewModel’s routeData.page property is "home". If it is, render the home page’s content. If it’s not, it will render the chat messages page’s content with the {{else}} helper.
  • Use routeUrl(hashes) to create the right link URLs so that page will be set on route.data to either "home" or "chat".
• Update the chat-app component's ViewModel to:
  • Setup a connection between the route.data state and the ViewModel’s routeData property by:
    • Defining a routeData property with a default value that returns the route.data.
    • Create a pretty routing rule so if the URL looks like "#!chat", the page property of route.data will be set to chat with register. If there is nothing in the hash, page will be set to "home".
    • Initialize the url’s values on route.data and set up the two-way connection with start.

import { Component, route } from "//unpkg.com/can@5/core.mjs";

Component.extend({
    tag: "chat-app",
    view: `
        <div class="container">
            <div class="row">
                <div class="col-sm-8 col-sm-offset-2">
                    {{# eq(this.routeData.page, 'home') }}
                        <h1 class="page-header text-center" on:click="this.addExcitement()">
                            {{ this.message }}
                        </h1>
                        <a href="{{ routeUrl(page='chat') }}"
                            class="btn btn-primary btn-block btn-lg">
                            Start chat
                        </a>
                    {{ else }}
                     <h1 class="page-header text-center">
                        Chat Messages
                    </h1>
                    <h5><a href="{{ routeUrl(page='home') }}">Home</a></h5>
                    {{/ eq }}
                </div>
            </div>
        </div>`,
    ViewModel: {
        // Properties
        message: {
            type: "string",
            default: "Chat Home"
        },
        routeData: {
            default(){
                route.register("{page}",{page: "home"});
                route.start();
                return route.data;
            }
        },
        // Methods
        addExcitement(){
            this.message = this.message + "!";
        }
    }
});

When complete, you should be able to toggle between the two pages. If you type:

window.location.hash

in CodePen’s console tab after clicking a new page, you will be able to see the hash change between !# and #!chat.

This step sets up basic routing between different “pages” in an application. CanJS’s routing is based on the values accessible to the application ViewModel. When those properties change, different content is shown.

We connected the application ViewModel to the routing system by having the ViewModel's routeData property return can-route.data. We initialized that connection between can-route.data and the url with can-route.start.

This makes it so if the routeData.page property changes, the browser’s URL will change. If the browser’s URL changes, the routeData.page property changes.

Key take-away: can-route two-way binds changes in the browser’s URL to the application ViewModel and vice versa. Use changes in the application ViewModel to control which content is shown.

Chat Messages Component

In this section, we will:

• Define and use a custom <chat-messages> element that contains the behavior of the chat messages page.

Update the JavaScript panel to:

• Define a <chat-messages> custom element with can-component. It's view will contain the content of the chat messages page.
• Update <chat-app>’s view to create a <chat-messages> element.

import { Component, route } from "//unpkg.com/can@5/core.mjs";

Component.extend({
    tag: "chat-messages",
    view: `
        <h1 class="page-header text-center">
            Chat Messages
        </h1>
        <h5><a href="{{ routeUrl(page='home') }}">Home</a></h5>`
});

Component.extend({
    tag: "chat-app",
    view: `
        <div class="container">
            <div class="row">
                <div class="col-sm-8 col-sm-offset-2">
                    {{# eq(this.routeData.page, 'home') }}
                        <h1 class="page-header text-center" on:click="this.addExcitement()">
                            {{ this.message }}
                        </h1>
                        <a href="{{ routeUrl(page='chat') }}"
                            class="btn btn-primary btn-block btn-lg">
                            Start chat
                        </a>
                    {{ else }}
                        <chat-messages/>
                    {{/ eq }}
                </div>
            </div>
        </div>`,
    ViewModel: {
        // Properties
        message: {
            type: "string",
            default: "Chat Home"
        },
        routeData: {
            default(){
                route.register("{page}",{page: "home"});
                route.start();
                return route.data;
            }
        },
        // Methods
        addExcitement(){
            this.message = this.message + "!";
        }
    }
});

When complete, you should see the same behavior as the previous step. You should be able to click back and forth between the two different pages.

This step creates the <chat-messages> custom element. Custom elements are used to represent some grouping of related (and typically visual) functionality such as:

• Widgets like <my-slider> or <acme-navigation>.
• Pages like <chat-login> or <chat-messages>.

Custom elements are the macroscopic building blocks of an application. They are the orchestration pieces used to assemble the application into a whole.

For example, an application’s template might assemble many custom elements to work together like:

{{# if(session) }}
  <app-toolbar selectedFiles:bind="selectedFiles"/>
  <app-directory selectedFiles:bind="selectedFiles"/>
  <app-files selectedFiles:bind="selectedFiles"/>
  <app-file-details selectedFiles:bind="selectedFiles"/>
{{ else }}
  <app-login/>
{{/ if }}

Breaking down an application into many isolated and potentially reusable components is a critical piece of CanJS software architecture.

Custom elements are defined with can-component. Components render their view with a ViewModel instance. By default, their view only has access to the data in the ViewModel. You can use event and data bindings like key:from and key:bind to pass data between custom elements.

Key take-away: can-component makes custom elements. Break down your application into many bite-sized custom elements.

List Messages

In this section, we will:

• Display messages from https://chat.donejs.com/api/messages when messagesPromise.isResolved.
• Show a “Loading…” message while the messages are loading (messagesPromise.isPending).
• Show an error if those messages fail to load (messagesPromise.isRejected).

Update the JavaScript panel to:

• Define a Message type with can-define/map/map.
• Define a Message.List type that contains Message items.
• Connect the Message and Message.List type to the RESTful messages service at https://chat.donejs.com/api/messages using can-realtime-rest-model.
• Update the <chat-messages>’s view to:
  • Check if the messages are in the process of loading and show a loading indicator.
  • Check if the messages failed to load and display the reason for the failure.
  • If messages successfully loaded, list each message’s name and body. If there are no messages, write out “No messages”.
• Update the <chat-messages>’s ViewModel to:
  • Define a messagesPromise property on ChatMessagesVM that’s default is initialized to a Promise that represents the loading of all messages using getList.

import { Component, route, DefineMap, DefineList, realtimeRestModel } from "//unpkg.com/can@5/core.mjs";

const Message = DefineMap.extend("Message",{
    id: "number",
    name: "string",
    body: "string",
    created_at: "date"
});

Message.List = DefineList.extend("MessageList",{
    "#": Message
});

Message.connection = realtimeRestModel({
    url: {
        resource: 'https://chat.donejs.com/api/messages',
        contentType: 'application/x-www-form-urlencoded'
    },
    Map: Message,
    List: Message.List
});

Component.extend({
    tag: "chat-messages",
    view: `
        <h1 class="page-header text-center">
            Chat Messages
        </h1>
        <h5><a href="{{ routeUrl(page='home') }}">Home</a></h5>

        {{# if(this.messagesPromise.isPending) }}
            <div class="list-group-item list-group-item-info">
                <h4 class="list-group-item-heading">Loading…</h4>
            </div>
        {{/ if }}
        {{# if(this.messagesPromise.isRejected) }}
            <div class="list-group-item list-group-item-danger">
                <h4 class="list-group3-item-heading">Error</h4>
                <p class="list-group-item-text">{{ this.messagesPromise.reason }}</p>
            </div>
        {{/ if }}
        {{# if(this.messagesPromise.isResolved) }}
            {{# for(message of this.messagesPromise.value) }}
                <div class="list-group-item">
                    <h4 class="list-group3--item-heading">{{ message.name }}</h4>
                    <p class="list-group-item-text">{{ message.body }}</p>
                </div>
            {{ else }}
                <div class="list-group-item">
                    <h4 class="list-group-item-heading">No messages</h4>
                </div>
            {{/ for }}
        {{/ if }}`,
    ViewModel: {
        // Properties
        messagesPromise: {
            default(){
                return Message.getList({});
            }
        }
    }
});

Component.extend({
    tag: "chat-app",
    view: `
        <div class="container">
            <div class="row">
            <div class="col-sm-8 col-sm-offset-2">
                {{# eq(this.routeData.page, 'home') }}
                    <h1 class="page-header text-center" on:click="this.addExcitement()">
                        {{ this.message }}
                    </h1>
                    <a href="{{ routeUrl(page='chat') }}"
                     class="btn btn-primary btn-block btn-lg">
                        Start chat
                    </a>
                {{ else }}
                 <chat-messages/>
                {{/ eq }}
            </div>
            </div>
        </div>`,
    ViewModel: {
        // Properties
        message: {
            type: "string",
            default: "Chat Home"
        },
        routeData: {
            default(){
                route.register("{page}",{page: "home"});
                route.start();
                return route.data;
            }
        },
        // Methods
        addExcitement(){
            this.message = this.message + "!";
        }
    }
});

When complete, you should see a list of messages in the chat messages page.

This step creates a Message model by first creating the Message type and then connecting it to a messages service at https://chat.donejs.com/api/messages.

Explanation

The can-realtime-rest-model mixin adds methods to the Message type that let you:

• Get a list of messages:

  Message.getList({}).then(function(messages){})
  

• Get a single message:

  Message.get({id: 5}).then(function(message){})
  

• Create a message on the server:

  message = new Message({name: "You", body: "Hello World"})
  message.save()
  

• Update a message on the server:

  message.body = "Welcome Earth!";
  message.save();
  

• Delete message on the server:

  message.destroy();
  

There are also methods to let you know when a message isNew, isSaving, and isDestroying.

With the message model created, it’s used to load and list messages on the server.

Key take-away: Create a model for your data’s schema and use it to communicate with a backend server.

Create Messages

In this section, we will:

• Add the ability to create messages on the server and have them added to the list of messages.

Update the <chat-messages> view to:

• Create a form to enter a message’s name and body.
• When the form is submitted, call send on the ChatMessagesVM with on:event.
• Connect the first <input>’s value to the ChatMessagesVM’s name property with key:bind.
• Connect the second <input>’s value to the ChatMessagesVM’s body property with key:bind.

Update the <chat-messages> ViewModel to:

• Define a name and body property on ChatMessagesVM.
• Define a send method on ChatMessagesVM that creates a new Message and sends it to the server.

import { Component, route, DefineMap, DefineList, realtimeRestModel } from "//unpkg.com/can@5/core.mjs";

const Message = DefineMap.extend("Message",{
    id: "number",
    name: "string",
    body: "string",
    created_at: "date"
});

Message.List = DefineList.extend("MessageList",{
    "#": Message
});

Message.connection = realtimeRestModel({
    url: {
        resource: 'https://chat.donejs.com/api/messages',
        contentType: 'application/x-www-form-urlencoded'
    },
    Map: Message,
    List: Message.List
});

Component.extend({
    tag: "chat-messages",
    view: `
        <h1 class="page-header text-center">
            Chat Messages
        </h1>
        <h5><a href="{{ routeUrl(page='home') }}">Home</a></h5>

        {{# if(this.messagesPromise.isPending) }}
            <div class="list-group-item list-group-item-info">
                <h4 class="list-group-item-heading">Loading…</h4>
            </div>
        {{/ if }}
        {{# if(this.messagesPromise.isRejected) }}
            <div class="list-group-item list-group-item-danger">
                <h4 class="list-group3-item-heading">Error</h4>
                <p class="list-group-item-text">{{ this.messagesPromise.reason }}</p>
            </div>
        {{/ if }}
        {{# if(this.messagesPromise.isResolved) }}
            {{# for(message of this.messagesPromise.value) }}
                <div class="list-group-item">
                    <h4 class="list-group3--item-heading">{{ message.name }}</h4>
                    <p class="list-group-item-text">{{ message.body }}</p>
                </div>
            {{ else }}
                <div class="list-group-item">
                    <h4 class="list-group-item-heading">No messages</h4>
                </div>
            {{/ for }}
        {{/ if }}

        <form class="row" on:submit="this.send(scope.event)">
                <div class="col-sm-3">
                    <input type="text" class="form-control" placeholder="Your name"
                                 value:bind="this.name"/>
                </div>
                <div class="col-sm-6">
                    <input type="text" class="form-control" placeholder="Your message"
                                 value:bind="this.body"/>
                </div>
                <div class="col-sm-3">
                    <input type="submit" class="btn btn-primary btn-block" value="Send"/>
                </div>
        </form>`,
    ViewModel: {
        // Properties
        messagesPromise: {
            default(){
                return Message.getList({});
            }
        },
        name: "string",
        body: "string",

        // Methods
        send(event) {
            event.preventDefault();

            new Message({
                name: this.name,
                body: this.body
            }).save().then(() => {
                this.body = "";
            });
        }
    }
});

Component.extend({
    tag: "chat-app",
    view: `
        <div class="container">
            <div class="row">
            <div class="col-sm-8 col-sm-offset-2">
                {{# eq(this.routeData.page, 'home') }}
                    <h1 class="page-header text-center" on:click="this.addExcitement()">
                        {{ this.message }}
                    </h1>
                    <a href="{{ routeUrl(page='chat') }}"
                     class="btn btn-primary btn-block btn-lg">
                         Start chat
                    </a>
                {{ else }}
                 <chat-messages/>
                {{/ eq }}
            </div>
            </div>
        </div>`,
    ViewModel: {
        // Properties
        message: {
            type: "string",
            default: "Chat Home"
        },
        routeData: {
            default(){
                route.register("{page}",{page: "home"});
                route.start();
                return route.data;
            }
        },
        // Methods
        addExcitement(){
            this.message = this.message + "!";
        }
    }
});

When complete, you will be able to create messages and have them appear in the list.

This step sets up a form to create a Message on the server. Notice that the new Message automatically appears in the list of messages. This is because can-realtime-rest-model adds the real-time behavior. The real-time behavior automatically inserts newly created messages into lists that they belong within. This is one of CanJS’s best features — automatic list management.

Key take-away: CanJS will add, remove, and update lists for you automatically.

Real Time

In this section, we will:

• Listen to messages created by other users and add them to the list of messages.

Update the JavaScript panel to:

• Create a https://socket.io/ connection (socket).
• Listen for when messages are created, updated, and destroyed, and call the corresponding real-time methods.

import { Component, route, DefineMap, DefineList, realtimeRestModel } from "//unpkg.com/can@5/core.mjs";

const Message = DefineMap.extend("Message",{
    id: "number",
    name: "string",
    body: "string",
    created_at: "date"
});

Message.List = DefineList.extend("MessageList",{
    "#": Message
});

Message.connection = realtimeRestModel({
    url: {
        resource: 'https://chat.donejs.com/api/messages',
        contentType: 'application/x-www-form-urlencoded'
    },
    Map: Message,
    List: Message.List
});

const socket = io('https://chat.donejs.com');

socket.on('messages created', function(message){
    Message.connection.createInstance(message);
});
socket.on('messages updated', function(message){
    Message.connection.updateInstance(message);
});
socket.on('messages removed', function(message){
    Message.connection.destroyInstance(message);
});

Component.extend({
    tag: "chat-messages",
    view: `
        <h1 class="page-header text-center">
             Chat Messages
        </h1>
        <h5><a href="{{ routeUrl(page='home') }}">Home</a></h5>

        {{# if(this.messagesPromise.isPending) }}
            <div class="list-group-item list-group-item-info">
                <h4 class="list-group-item-heading">Loading…</h4>
            </div>
        {{/ if }}
        {{# if(this.messagesPromise.isRejected) }}
            <div class="list-group-item list-group-item-danger">
                <h4 class="list-group3-item-heading">Error</h4>
                <p class="list-group-item-text">{{ this.messagesPromise.reason }}</p>
            </div>
        {{/ if }}
        {{# if(this.messagesPromise.isResolved) }}
            {{# for(message of this.messagesPromise.value) }}
                <div class="list-group-item">
                    <h4 class="list-group3--item-heading">{{ message.name }}</h4>
                    <p class="list-group-item-text">{{ message.body }}</p>
                </div>
            {{ else }}
                <div class="list-group-item">
                    <h4 class="list-group-item-heading">No messages</h4>
                </div>
            {{/ for }}
        {{/ if }}

        <form class="row" on:submit="this.send(scope.event)">
            <div class="col-sm-3">
                <input type="text" class="form-control" placeholder="Your name"
                    value:bind="this.name"/>
            </div>
            <div class="col-sm-6">
                <input type="text" class="form-control" placeholder="Your message"
                    value:bind="this.body"/>
            </div>
            <div class="col-sm-3">
                <input type="submit" class="btn btn-primary btn-block" value="Send"/>
            </div>
        </form>`,
    ViewModel: {
        // Properties
        messagesPromise: {
            default(){
                return Message.getList({});
            }
        },
        name: "string",
        body: "string",

        // Methods
        send(event) {
            event.preventDefault();

            new Message({
                name: this.name,
                body: this.body
            }).save().then(() => {
                this.body = "";
            });
        }
    }
});

Component.extend({
    tag: "chat-app",
    view: `
        <div class="container">
            <div class="row">
                <div class="col-sm-8 col-sm-offset-2">
                    {{# eq(this.routeData.page, 'home') }}
                        <h1 class="page-header text-center" on:click="this.addExcitement()">
                            {{ this.message }}
                        </h1>
                        <a href="{{ routeUrl(page='chat') }}"
                            class="btn btn-primary btn-block btn-lg">
                            Start chat
                        </a>
                    {{ else }}
                        <chat-messages/>
                    {{/ eq }}
                </div>
            </div>
        </div>`,
    ViewModel: {
        // Properties
        message: {
            type: "string",
            default: "Chat Home"
        },
        routeData: {
            default(){
                route.register("{page}",{page: "home"});
                route.start();
                return route.data;
            }
        },
        // Methods
        addExcitement(){
            this.message = this.message + "!";
        }
    }
});

When complete, you can open up the same CodePen in another window, create a message, and it will appear in the first CodePen’s messages list.

This step connects to a WebSocket API that pushes messages when Messages are created, updated or destroyed. By calling the real-time methods when these events happen, CanJS will automatically update the messages list.

Key take-away: CanJS will add, remove, and update lists for you automatically. It’s awesome!

Result

When finished, you should see something like the following CodePen:

See the Pen CanJS 5.0 Chat - Final by Bitovi (@bitovi) on CodePen.