This tutorial will build an extremely simple seed project with Angular2. We will begin with the most basic application possible and then add on a bit more functionality.

Angular 2 applications are built by creating HTML templates that contain angular specific markup. Classes are then created to manage the templates and everything is wrapped into a module, which you piece together to create your application. These modules are referred to as components.

Angular interprets these modules and uses them to present your application in the browser.

Let's get started with a minimal application. We will begin with an application that contains a single module whose only job is to display some text.

We will begin by creating a new folder called "app".

$ mkdir app

As mentioned above, our application will begin with a single module, or component, that will display some text to the screen. We can use both pure JavaScript or TypeScript to make an angular 2 app. Using TypeScript, it is easier and more programmer friendly 😉

Let's learn how to create a component using TypeScript.

Create a file called app.component.ts as shown:

    // app.component.ts
    
    import { Component } from '@angular/core';
    @Component({
      selector: 'my-app',
      template: '<h1>Free Code Camp Rocks!</h1>',
      styles: [`
        h1 { color: darkgreen; font-family: Arial, Helvetica, sans-serif;}
      `]
    })
    export class AppComponent { }

Every Angular 2 application has at least one component which is usually named AppComponent. A component manages a portion of the page using the template within it.

Our component demonstrates the basic structure of any component you will ever write. It contains:

• import statements to pull in other components we will need
• component decorator which lets angular know which template to use and how the component will be created. Basically, any meta data related to the component.
• component class which controls the component's appearance and behavior

Let's take a closer look at each line in our component.

##Import

import { Component } from '@angular/core';

Since angular applications are modular, we can import any other modules or libraries we may need. Here, we are importing the Angular 2 core module to give our component access to the @Component decorator. Every app will need this import to get started.

Since we imported the Component function above, we can now use it to associate metadata with our component class that will tell Angular how our component should be created and the actions it will provide.

    @Component({
      selector: 'my-app',
      template: '<h1>Free Code Camp Rocks!</h1>'
    })

Our metadata object has selector and template fields.

• The selector specifies a CSS selector that indicates which HTML element will represent this component. The element we will use will be named "my-app". Angular will use this to create an instance of our component where it finds this element.
• The template tells angular what template it will use for this component. This can refer to other Components or just a form of HTML that tells how to display the view for our component. Our template is just displaying an h1 element containing the text "Free Code Camp Rocks!".

Our final line provides an empty class named AppComponent

export class AppComponent { }

If we want to build a more complex component we can add logic and properties to the class. This component is extremely basic and simply displays some html, so its class will remain empty.

We export our class so we can use it in other components in our application.

Next, we need to connect our root component to Angular. To do this we create another file in our app folder called main.ts that will have the following code:

    import { bootstrap }    from '@angular/platform-browser-dynamic';
    import { AppComponent } from './app.component';
    bootstrap(AppComponent);

This file imports the two items we need to start our app.

• bootstrap - Angular's built in method that connects to the browser
• AppComponent - Our component we created above (which is why we exported it) We then call bootstrap method with AppComponent

Finally, create index.html

    <html>
      <head>
        <title>Free Code Camp - Angular 2 Tutorial</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <link rel="stylesheet" href="styles.css">
        <!-- 1. Load libraries -->
        <script src="https://npmcdn.com/core-js/client/shim.min.js"></script>

        <script src="https://npmcdn.com/[email protected]?main=browser"></script>
        <script src="https://npmcdn.com/[email protected]"></script>
        <script src="https://npmcdn.com/[email protected]/dist/system.src.js"></script>
        
        <!-- 2. Configure SystemJS -->
        <script src="systemjs.config.js"></script>
        <script>
          System.import('app').catch(function(err){ console.error(err); });
        </script>
      </head>
      
      <!-- Display app in my-app element -->
      <body>
        <my-app>Loading Your App...</my-app>
      </body>
    </html>

In commented section 1, we loaded several libraries that improve the compatibility of this tutorial with different browsers/versions. It also imports system.src.js which is used as module loader to import the app.

In section 2, SystemJS is used to load our application and our various modules. In a production example we may want to use something else such as webpack. It was chosen here since we can use it with plunker.

This is all that is required to get our simple application running. Here is a link to a plunker that contains our working application. You can fork it into your own version and change whatever you'd like.

VIEW APP

Now let's add a bit more functionality to our program. We will create a counter that let's you increment it by clicking a button.

Our increment component will be its own module so that we can reuse it in later applications.

Let's name our file: app/increment-clicker.component.ts and set it up.

// app/increment-clicker.component.ts
import { Component } from '@angular/core'; 

@Component({
    selector: 'increment-clicker',
    template: `
      <div className="counter">
        <h1>{{curClicks}} clicks</h1>
        <button type="button" (click)="incrementClicks()">Increment</button>
      </div>
    `,
    styles: [`
        .counter {
          width: 100%;
          margin: auto;
          background: darkgreen;
          border-radius: 5px;
          color: white;
          padding: 20px;
          text-align: center;
        }
        .counter h1 {
          margin: 0;
          padding: 20px;
          font-size: 36px;
        }
        .counter button {
          background: #f1c40f;
          border: 0;
          box-shadow: 0px 5px 0px #927608;
          padding: 20px;
          width: 100%;
          outline: none;
          border-radius: 5px;
          color: darkgreen;
          font-weight: bold;
        }
        
        .counter button:hover {
          background: #a9890a;
          cursor: pointer;
        }
    `]
})

export class IncrementClicker {
  curClicks = 0;
  
  incrementClicks() {
    this.curClicks++;
  }  
}

Our component structure is similar to our previous one, but we've added a bit of functionality here. You will notice our class is no longer empty. We've added a variable to track the clicks as well as a function to increment them when the user clicks the button.

You can display properties from your class in your template using double braces such as: {{ variableName }}

We bind the button click event to our class function using Angulars Event Bindings.

<button type="button" (click)="incrementClicks()">Increment</button>

Notice that we've also added some styling to our components. This way everything is self-contained in this module. You may also include a templateUrl and/or styleUrls properties instead to extract the template and style rules to an external file and link them here.

Now we just need to update our AppComponent to include our new component:

// app/app.component.ts

import { Component } from '@angular/core';

/* Nested Component */
import { IncrementClicker } from 'app/increment-clicker.component';

@Component({
  selector: 'my-app',
  directives: [IncrementClicker],
  template: `
    <h1>Free Code Camp Rocks!</h1>
    <increment-clicker></increment-clicker>
  `,
  styles: [`
    h1 { color: darkgreen; font-family: Arial, Helvetica, sans-serif;}
  `]  
})

export class AppComponent { }

To pull in our new IncrementClicker component we need to import it by including the class name as well as the location of the typescript file as we did on this line:

import { IncrementClicker } from 'app/increment-clicker.component';

We then add the IncrementClicker component as a directive to the AppComponent module using:

directives: [IncrementClicker],

Finally, we just add the tag that our component connects to in the template. So the selector in our IncrementClicker component will match the tag where we want it to show up.

  template: `
    <h1>Free Code Camp Rocks!</h1>
    <increment-clicker></increment-clicker>
  `,

Our component is now included in our app! Updated Code VIEW COMPLETE APPLICATION