NoGap

NoGap is a full-stack (spans Host and Client) JavaScript framework, featuring RPC (Remote Procedure Calls) + simple code sharing + basic asset management + full-stack Promise chains.

NoGap's primary use case is development of rich single-page web applications while alleviating the typical hassles of doing so.

This module is called No Gap because it removes the typical gap that exists between Host and Client and that makes a client-server-architecture so cumbersome to develop.

You probably want to start by having a look at the Samples for reference.

If you want to get serious, take a look at the Getting Started section to figure out how to build a complete Node-based web application with NoGap.

The Structure of NoGap components section lays out the structure of NoGap's basic building block: the component.

Note that currently, the only dependency of NoGap is Node and some of its modules but even that is planned to be removed in the future.

NOTE: NoGap is still in Beta. Things are still changing. If you are concerned about that, feel free to contact me directly.

Table of Contents

• NoGap
• HelloWorld
• Installation
• Samples
  • HelloWorld
  • TwoWayStreet
  • Full-stack promise chains
  • TwoWayStreetAsync
  • CodeSharingValidation
  • Assets
  • Multiple Components
  • Full-stack error handling
  • Dynamic Loading of Components
  • Simple Sample App
• Component Structure
  • Host
  • Client
  • Base
  • Component Skeleton
• Getting Started
  • Recommended File Structure
    • components/
    • components/models/
    • components/ui/
    • components/util/
    • app.js
    • appConfig.js
    • package.json
• Debuggability & security
• Important Terms
• Final Words

HelloWorld

Link.

var NoGapDef = require('nogap').Def;

module.exports = NoGapDef.component({
  Client: NoGapDef.defHost(function(Tools, Instance, Context) {
    return {
      initClient: function() {
        document.body.innerHTML = 'Hello World!';
      }
    };
  });
});

Concepts

• Get the NoGap module's Def helper: var NoGapDef = require('nogap').Def;
• Define a new component: NoGapDef.component({ ... });
• Add a Client definition to the component: Client: NoGapDef.defClient(function(Tools, Instance, Context) { ... })
• Add initClient method to Client

What is the trick?

• The Client code is automatically deployed to the client
• initClient is then automatically called on the client, right afterwards

Installation

• Install Node
  • Make sure to select Add to PATH during GUI-based installation.
• Open a command line
  • On Windows: Press Ctrl+R -> Type cmd -> Enter
• Run: npm install nogap
• Done.

Samples

Link.

The Samples highlight some (soon, all!) features of the NoGap framework and how they are used. To run the samples:

1. Create a new folder (e.g. NoGapTest)
2. Follow installation instructions given above
   • You now have a node_modules/nogap subfolder.
   • You can now work through the samples below and try it out in real-time
3. cd node_modules/nogap/samples/HelloWorld (or any other sample)
4. npm install (will automatically download and install the sample's dependencies)
5. npm start (this will run the app defined in the sample's package.json)
6. Open your browser and go to localhost:1234 (or whatever port you are using)
7. Start playing!

HelloWorld

Link.

var NoGapDef = require('nogap').Def;

module.exports = NoGapDef.component({
  Client: NoGapDef.defClient(function(Tools, Instance, Context) {
    return {
      initClient: function() {
        document.body.innerHTML = 'Hello World!';
      }
    };
  });
});

Concepts

• Get the NoGap module's Def helper: var NoGapDef = require('nogap').Def;
• Define a new component: NoGapDef.component({ ... });
• Add a Client definition to the component: Client: NoGapDef.defClient(function(Tools, Instance, Context) { ... })
• Add initClient method to Client

What is the trick?

• The Client code is automatically deployed to the client
• initClient is then automatically called on the client, right after installation

TwoWayStreet

Link.

var NoGapDef = require('nogap').Def;

NoGapDef.component({
    Host: NoGapDef.defHost(function(SharedTools, Shared, SharedContext) {
        var nBytes = 0;

        return {
            Public: {
                tellMeSomething: function(message) {
                    nBytes += (message && message.length) || 0;
                    this.client.showHostMessage('Host has received a total of ' + nBytes + ' bytes.');
                }
            }
        };
    }),

    Client: NoGapDef.defClient(function(Tools, Instance, Context) {
        return {
            initClient: function() {
                // bind a button to a component function (quick + dirty):
                window.clickMe = this.onButtonClick.bind(this);
                document.body.innerHTML += '<button onclick="window.clickMe();">Click Me!</button><br />';
            },

            onButtonClick: function() {
                document.body.innerHTML +='Button was clicked.<br />';
                this.host.tellMeSomething('hello!');
            },

            Public: {
                showHostMessage: function(msg) {
                    document.body.innerHTML +='Server said: ' + msg + '<br />';
                }
            }
        };
    })
});

Concepts

• Add a Client definition to the component: Client: NoGapDef.defClient(function(Tools, Instance, Context) { ... })
• Client.initClient
• Add a Host definition to the component: Host: NoGapDef.defHost(function(SharedTools, Shared, SharedContext) { ... })
• Host.Public
• Client.Public

What is the trick?

• this.host gives us an object on which we can call Public methods on the host
• For example, we can call tellMeSomething which is a method that was defined in Host.Public
• Once the host receives our request, it calls this.client.showHostMessage
• Note: this.host (available on Client) vs. this.client (available on Host)

Full-stack promise chains

NoGap supports full-stack Promise chains. Meaning you can let the Client wait until a Host-side function call has returned. And you can even return a value from a Host function, and it will arrive at the Client. Errors also traverse the entire stack!

Code snippet:

var NoGapDef = require('nogap').Def;

NoGapDef.component({
    Host: NoGapDef.defHost(function(SharedTools, Shared, SharedContext) {
        var nBytes = 0;

        return {
            Public: {
                tellMeSomething: function(message) {
				    nBytes += (message && message.length) || 0;
				    this.Tools.log('Client said: ' + message);
				    return 'Thank you! I now received a total of ' + nBytes + ' bytes.';
                }
            }
        };
    }),

    Client: NoGapDef.defClient(function(Tools, Instance, Context) {
        return {
            initClient: function() {
                // bind a button to a component function (quick + dirty):
                window.clickMe = this.onButtonClick.bind(this);
                document.body.innerHTML += '<button onclick="window.clickMe();">Click Me!</button><br />';
            },

            onButtonClick: function() {
			    document.body.innerHTML +='Button was clicked.<br />';
			    this.host.tellMeSomething('hello!')
			    .then(function(hostMessage) {
			    	document.body.innerHTML += 'Host said: ' + hostMessage + '<br />';
			    })
			    .catch(function(err) {
			    	// this can be a connection error, a bug, a Host-side `reject` etc etc...
			    	console.error('Something went wrong: ' + (err.stack || err));
			    });
            }
        };
    })
});

New Concepts

• Client.initClient will be called right after the Client connected.
• Upon button click, we call this.host.tellMeSomething(...) which will send a request to the Host to invoke that method (given it is in Host.Public).
• Calling a Public function on a component's host object returns a promise.
• That promise is part of a full-stack Promise chains. Once finnished, we get the return value from that Host method in our then callback.

TwoWayStreetAsync

Link.

Imagine the server had to do an asynchronous operation in tellMeSomething, such as reading a file, or getting something from the database.

We can simply use promises for that!

tellMeSomething: function() {
    Promise.delay(500)    // wait 500 milliseconds before replying
    .bind(this)           // this is tricky!
    .then(function() {
        this.client.showHostMessage('We have exchanged ' + ++iAttempt + ' messages.');
    });
}

And again, we can just return the message and it will arrive at the Client automagically, like so:

tellMeSomething: function() {
    Promise.delay(500)    // wait 500 milliseconds before replying
    .bind(this)           // this is tricky!
    .then(function() {
        return 'We have exchanged ' + ++iAttempt + ' messages.';
    });
}

// ...

onButtonClick: function() {
    document.body.innerHTML +='Button was clicked.<br />';
    this.host.tellMeSomething()
    .bind(this)           // this is tricky!
    .then(function(hostMessage) {
        this.showHostMessage(hostMessage);
    });
},

New Concepts

• We need to perform an asynchronous request whose result is to be sent to the other side
• Simply use Promise chains!
• NOTE: JavaScript's this is tricky!

CodeSharingValidation

Link.

  Base: NoGapDef.defBase(function(SharedTools, Shared, SharedContext) { return {
      validateText: function(text) {
          if (text.indexOf('a') >= 0 || text.indexOf('A') >= 0) {
              return null;
          }
          return text.trim();
      }
  };}),

    Host: NoGapDef.defHost(function(SharedTools, Shared, SharedContext) { return {
        Public: {
            setValue: function(value) {
                this.value = this.Shared.validateText(value);
                // ...
            }
        }
    };}),

    Client: NoGapDef.defClient(function(Tools, Instance, Context) { return {
          // ...
                    value = this.validateText(value);
            // ...
    };})

New Concepts

• The Base definition is merged into both Client and Host
• You can use it to easily share code between them

Assets

Link.

NoGapDef.component({
    Host: NoGapDef.defHost(function(SharedTools, Shared, SharedContext) { return {
        Assets: {
            AutoIncludes: {
                js: [
                    // jquery
                    '//ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js'
                ],

                css: [
                    // bootstrap
                    '//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css'
                ]
            },

            Files: {
                string: {
                    /**
                     * The contents of `template.html` will be automatically made available to the client
                     * through in the `assets.view` property.
                     */
                    view: 'template.html'
                }
            }
        }
    };}),

    Client: NoGapDef.defClient(function(Tools, Instance, Context) { return {
        initClient: function() {
            /**
             * Append contents of HTML asset to document.
             */
            document.body.innerHTML += this.assets.view;
        }
    };})
});

New Concepts

• As of now, you can define two types of file-based assets:
  • AutoIncludes defines lists of js and css files that will be automatically included in the client header
  • Files will be read and it's contents will be available through the clients assets variable.
    • Currently they can only be interpreted as string. Future plans: code, image and more more more...

Multiple Components

The Simple Sample App already does this.

Examples of multi-component code

• Call say on ComponentA: Shared.ComponentA.say('hello');
• Call somePublicMethod on the client of a ComponentB instance: this.Instance.ComponentB.client.somePublicMethod(some, data);

Full-stack error handling

TODO!

• Feel free to try and throw an error or use Promise.reject in a Host's Public function, and then catch it on the Client side. You will notice that, for security reasons, the contents of Host-side exceptions are modified before being sent to the Client.
• You can override Tools.onError to customize error handling (especially on the server)
• TODO: Trace verbosity configuration

Dynamic Loading of Components

This feature lets clients request components on demand. This way, complex web applications can send code and assets at the time of first usage, not one moment earlier. This saves bandwidth and improves I/O performance.

How?

1. Set lazyLoad to 1 in the config
2. Call this.Tools.requestClientComponents(componentNames, callback); to lazily load components from Host or from Client instances.

Simple Sample App

Link.

This App shows how to start building a real application with NoGap. It uses Angular, Boostrap and Font-Awesome to do some real client-side rendering and client<->host communication. IMPORTANT: None of these libraries are required. You can build your frontend and backend any way you want.

Component Structure

NOTE: The following is a rough explanation of many of NoGap's features. You are recommended to compare the explanation to their actual implementation in the Simple Sample App to better understand them.

Every component has two endpoint definitions, called Host and Client, as well as shared code, inside the so-called Base definition. You provide Host, Client and Base definitions by calling defHost, defClient and defBase respectively. The only argument to these def* functions is your component definition: A function with three arguments that returns the actual definition object.

Host

Host has two places for defining functionality: Shared and instance. This distinction is necessary because a Host can be tied to multiple Clients. Note though that each Client can only be tied to a single Host (as of now).

1. The Shared object of a component is a singleton; it exists only once for the entire application. You can access all Shared component objects through the Shared set which is the second argument of every Host's component definition.

2. The instance object of a component exists once for every client. Every client that connects to the server, gets its own set of instances of every active component. On the Host side, the instance object of a component is defined as the merged result of all members of Private and Public which we call instance members. These instance members are accessible through this.Instance from instance code, that is, code inside of Private and Public properties. If you want to hook into client connection and component bootstrapping events, simply define onNewClient or onClientBootstrap functions inside Host.Private. You can access the owning component's Shared singleton through this.Shared from within Private or Public functions. Inside a Host instance object, you can directly call Public instance members on the client through this.client.someClientPublicMethod(some, data). Being able to directly call a function on a different computer or in a different program is called RPC (Remote Procedure Call). Similarly, Client instances can directly call this.host.someHostPublicMethod which returns a Promise which will be fulfilled once the Host has run the function and notified the client.

Client

The set of all Client endpoint definitions is automatically sent to the client and installed, as soon as a client connects. On the client side, this.Shared and this.Instance refer to the same object, and Private and Public are both merged into the Client component definition itself. If you want to load components dynamically (i.e. lazily), you need to set the lazyLoad config parameter to true or 1.

Base

Everything from the Base definition is merged into both, Host and Client. Public and Private are also merged correspondingly. Since Host and Client operate slightly different, certain naming decisions had to be made seemingly in favor of one over the other. E.g. the Shared concept does not exist on client side (because a Client only contains a single instance of all components), so there, it simply is the same as Instance. Inside Base members, you can call this.someMethod even if someMethod is not declared in Base, but instead is declared in Host as well as Client. At the same time, you can call this.someBaseMethod from Client or Host. That enables you to easily have shared code call endpoint-specific code and vice versa, thereby supporting polymorphism and encapsulation.

Component Skeleton

This skeleton code summarizes (most of) the available component structure:

/**
 * A complete Component skeleton
 */
"use strict";

var NoGapDef = require('nogap').Def;

module.exports = NoGapDef.component({
    /**
     * If no name is given, NoGap will use the filename as name.
     * If you define more than one unnamed component per file, you will see an error.
     */
    Name: undefined,

    /**
     * Array of names (strings) of all components to also be installed 
     * when installing this component.
     * This is to signal that one component depends on or 
     * requires use of another.
     * NOTE: This is important when components are dynamically loaded (`lazyLoad` = 1).
     */
    Includes: [ 'Component1', 'SomethingElse' ],

    /**
     * The `Base` definition is merged into both, `Host` and `Client`
     */
    Base: NoGapDef.defBase(function(SharedTools, Shared, SharedContext) {
        return {
            /**
             * Called right before `__ctor` of `Host` and `Client`.
             * Will be removed once called.
             */
            __ctor: function() {
            },

            /**
             * Called right before `initHost` and `initClient`.
             */
            initBase: function() {
            },

            /**
             * Private instance members.
             */
            Private: {
            },

            /**
             * Public instance methods that can be called by the other side.
             */
            Public: {
            }
        };
    }),

    /**
     * The `Host` definition is only executed on and visible to the server.
     */
    Host: NoGapDef.defHost(function(SharedTools, Shared, SharedContext) {
        return {
            /**
             * The ctor is called only once, during NoGap initialization,
             * when the `Shared` component part is created.
             * Will be removed once called.
             */
            __ctor: function () {
            },
    
            /**
             * Is called once on each component after 
             * all components have been created, and after `initBase`.
             */
            initHost: function() {
            },

            /**
             * Private instance members.
             */
            Private: {
                /**
                 * Is called only once per session and application start, 
                 * when the instance for the given session has been created.
                 * Will be removed once called.
                 */
                __ctor: function () {
                },

                /**
                 * Called when a client connected.
                 */
                onNewClient: function() {
                },

                /**
                 * Called after `onNewClient`, once this component 
                 * is about to be sent to the `Client`.
                 * Since components can be deployed dynamically (if `lazyLoad` is enabled),
                 * this might happen much later, or never.
                 */
                onClientBootstrap: function() {
                }
            },

            /**
             * Public instance methods that can be called by the client.
             */
            Public: {
            },
        };
    }),

    /**
     * The `Client` definition is automatically deployed to every connected client.
     */
    Client: NoGapDef.defClient(function(Tools, Instance, Context) {
        return {
            /**
             * Called once after creation of the client-side instance.
             * Will be removed once called.
             */
            __ctor: function () {
            },

            /**
             * Called once after all currently deployed client-side 
             * components have been created, and after `initBase`.
             */
            initClient: function() {

            },

            /**
             * Called after the given component has been loaded in the Client.
             * NOTE: This is generally only important when components are dynamically loaded (`lazyLoad` = 1).
             *    (Because else, `initClient` will do the trick.)
             */
            onNewComponent: function(newComponent) {

            },

            /**
             * Called after the given batch of components has been loaded in the Client.
             * This is called after `onNewComponent` has been called 
             * on each individual component.
             * NOTE: This is generally only important when components are dynamically loaded (`lazyLoad` = 1).
             *    (Because else, `initClient` will do the trick.)
             */
            onNewComponents: function(newComponents) {

            },
            
            /**
             * This will be merged into the Client instance.
             * It's members will reside along-side the members defined above it.
             */
            Private: {
            },

            /**
             * Public instance methods that can be called by the host.
             */
            Public: {
            }
        };
    })
});

Getting Started

TODO: Need to rewrite this with to work with the new version that adapted full-stack Promises.

This tutorial is aimed at those who are new to NoGap, and new to Node in general. It should help you bridge the gap from the Code Snippets to a real-world application. Note that the Simple Sample App is also following these guidelines.

Recommended File Structure

.
+-- components/
| +-- models/
| +-- ui/
| +-- util/
+-- lib/
+-- pub/
+-- app.js
+-- appConfig.js
+-- package.json

This is the recommended file structure for the average web application. As always, the structure might look vastly different for special purpose applications.

components/

This folder contains your NoGap components, and possibly (some of) their assets. You can name it anything you want.

NOTE: Placing assets (such as *.html templates, stylesheets, images etc.) next to code is actually good style, if it supports modularization. If your components have a sufficiently modular design, you can simply copy their folder, to deploy them and their assets in other places.

components/models/

This folder contains the interface with your DB and possibly other storage systems. They provide CRUD functionality to the rest of the application.

components/ui/

This folder contains UI-related components. That is UI controller and view code. Views (templates and HTML files) are in files, separate from the code, but they can be in the same folder to support modularity.

components/util/

This folder contains general-purpose utility components used on both Client and Host. They usually only contain a Base definition, with possible specializations in Client and Host.

app.js

This defines your actual application. You can name it anything you want. Usually, this file only does three things:

1. Setup your app
2. Start NoGap
3. Start your express server

Express is the standard Node way of starting a HTTP server and let clients connect. Once it is running you can connect to it with your browser on the specified port.

NOTE: When using NoGap you will not need to work with express anymore (other than starting the server). You can use it, but you are recommended to use components instead.

appConfig.js

This is your custom configuration file. You can name it anything you want. It contains some basic constant data that your application needs, such as database login and other setup information. The following is an example of a NoGap configuration. It requires at least two entries:

• baseFolder

  • This is the folder, relative to your application (e.g. app.js) where you defined all NoGap components.

• files

• The actual component files (sans ".js"). Whenever you add a component, don't forget to list it here!

• Here is an example of a sample appConfig.js.

• Here is an example of a config file for a web app that controls an arbitrary amount of IOT devices which analyze and record WiFi SSID packets and send them to the server for analysis. The devices are controlled through the web interface. The devices also run NoGap to exchange data with the server, and also, to automatically update their code when new code is available and the devices is not busy or an admin forces an update through the web interface. The auto-updater is fault tolerant.

Optional Configuration parameters

• publicFolder (Default = pub/)
• The folder to find all client asset files that cannot be found relative to a component.
• Usually this is used to store client-only and shared javascript libraries that do not have NoGap support (they are not defined as components).
• lazyLoad (Default = true)
• Wether you want to explicitly send each component's client side to clients when necessary.
• endpointImplementation (set of options to configure the transport layer)
• name (Default = HttpPost)
  • Currently, only POST is available. Websockets will follow soon.
  • You can also implement your own transport layer if you want, but you probably don't.
  • If you are interested into the dirty details, have a look at HttpPostImpl in ComponentCommunications.js
• TODO: Tracing, logging + customized error handling

Example Config

"nogap": {
    "baseFolder"   : "components",
    "publicFolder" : "pub",
    "files"        : [
        // list all components here:

        // utilities
        "ValidationUtil",

        // pages for guests
        "Guest",

        // pages for users
        "Main",
        "Home"
    ]
}

package.json

This is the standard Node configuration file. Here you can declare your app's basic metadata and, most importantly, your dependencies. If you need one of the thousands over thousands of publicly available Node modules, two steps are required:

1. Add their name and your preferred version to dependencies
2. Run npm install

Done. Now the new module is available in your code via:

var someModule = require('some-module');

where some-module is the name you gave it in the package.json file.

Check out NPM JS to see all available modules.

Debuggability & security

By default, each Client only receives Client and Base definitions. Host-only code is not available to the client. However, the names of absolute file paths are sent to the client to facilitate perfect debugging; i.e. all stacktraces and the debugger will refer to the correct line inside the actual host-resident component file. If that is of concern to you, let me know, and I'll move up TODO priority of name scrambling, or have a look at ComponentDef's FactoryDef, and the corresponding def* methods yourself.

Important Terms

TODO: Add links + more terms.

• Component
• Host
• Client
• Endpoint (refers to Client or Host)
• Base (merged into Client and Host)
• Shared (set of all component singletons)
• Instance (set of all component instance objects, exist each once per connected client)
• Tools (set of functions to assist managing of components)
• Asset (an asset is content data, such as HTML and CSS code, images and more)
• more...

Final Words

Good luck! In case of any questions, feel free to contact me.