include _util-fns
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Good tools make application development quicker and easier to maintain than
if we did everything by hand.
The [**Angular-CLI**](https://cli.angular.io/) is a **_command line interface_** tool
that can create a project, add files, and perform a variety of on-going development tasks such
as testing, bundling, and deployment.
Our goal in this CLI QuickStart chapter is to build and run a super-simple Angular 2
application in TypeScript, using Angular-CLI
while adhering to the [Style Guide](./guide/style-guide.html) recommendations that
benefit _every_ Angular 2 project.
By the end of the chapter, we'll have a basic understanding of development with the CLI
and a foundation for both these documentation samples and our real world applications.
We'll pursue these ends in the following high-level steps:
1. [Set up](#devenv) the development environment
2. [Create](#create-proj) a new project and skeleton application
3. [Serve](#serve) the application
4. [Edit](#first-component) the application
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h2#devenv Step 1. Set up the Development Environment
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We need to set up our development environment before we can do anything.
Install **[Node.js® and npm](https://nodejs.org/en/download/)**
if they are not already on your machine.
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**Verify that you are running node `v4.x.x` and npm `3.x.x`**
by running `node -v` and `npm -v` in a terminal/console window.
Older versions produce errors.
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Then **install the [Angular-CLI](https://github.com/angular/angular-cli)** globally.
code-example(format="").
npm install -g angular-cli
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h2#create-project Step 2. Create a new project
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Open a terminal window.
.alert.is-important
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_Windows Developers_: open a console window _as an **administrator**_.
The Angular-CLI build steps later in this tutorial
create <a href="https://msdn.microsoft.com/en-us/library/windows/desktop/aa365680(v=vs.85).aspx" target="_blank"><i>symbolic links</i></a>
to various directories. These so-called _symlinks_ save time and space.
But it takes administrator rights under Windows to create them.
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Generate a new project and skeleton application by running the following commands:
code-example(format="").
ng new cli-quickstart
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Patience please.
It takes time to set up a new project, most of it spent installing npm packages.
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h2#serve Step 3: Serve the application
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Go to the project directory and launch the server.
code-example(format="").
cd cli-quickstart
ng serve
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The `ng serve` command launches the server, watches our files,
and rebuilds the app as we make changes to the files.
Open a browser on `http://localhost:4200/`; the app greets us with a message:
figure.image-display
img(src='/resources/images/devguide/cli-quickstart/app-works.png' alt="Our app works!")
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h2#first-component Step 4: Edit our first Angular component
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The CLI created our first Angular component for us.
This is the _root component_ and it is named after the project. We created the project
with the name `cli-quickstart` so our component is `CliQuickstartAppComponent` and
it's in the file `/src/app/cli-quickstart.component.ts`
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_CliQuickstartAppComponent_ is a _horrible name_. Almost everyone renames it to _AppComponent_ ...
and renames all of the associated files to _app.component.??_ as we do throughout the documentation.
We'll leave that step as an exercise.
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Open the component file and change the `title` property from _cli-quickstart works!_ to _My First Angular 2 App_:
+makeExample('cli-quickstart/ts/src/app/cli-quickstart.component.ts', 'title', 'src/app/cli-quickstart.component.ts')(format=".")
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The browser reloads automatically and we see the revised title. That's nice, but we can make it look better.
Open `src/app/cli-quickstart.component.css` and give our component some style
+makeExample('cli-quickstart/ts/src/app/cli-quickstart.component.css', null, 'src/app/cli-quickstart.component.css')(format=".")
figure.image-display
img(src='/resources/images/devguide/cli-quickstart/my-first-app.png' alt="Output of QuickStart app")
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Looking good!
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## What's next?
Our first application doesn't do much. It's basically "Hello, World" for Angular 2.
We kept it simple in our first pass: we wrote our first Angular 2 application using the angular CLI
and modified our first component. That's about all we'd expect to do for a "Hello, World" app.
**We have greater ambitions!**
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We're about to take the next step and build a small application that
demonstrates the great things we can build with Angular 2.
Join us on the [Tour of Heroes Tutorial](./tutorial)!
Or stick around a bit longer to learn a few things about what we just did.
<br><br>
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h1#behind-the-code Behind the code
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### CliQuickstartAppComponent is the root of the application
Every Angular app has at least one **root component**, that hosts the client user experience.
Components are the basic building blocks of Angular applications.
A component controls a portion of the screen — a *view* — through its associated template.
This QuickStart has only one, extremely simple component.
But it has the essential structure of every component we'll ever write:
* one or more [import](#component-import)
statements to reference the things we need.
* a [@Component decorator](#component-decorator)
that tells Angular what template to use and how to create the component.
* a [component class](#component-class)
that controls the appearance and behavior of a view through its template.
a#component-import
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### Import
Angular apps are modular. They consist of many files, each dedicated to a purpose.
Angular itself is modular. It is a collection of library modules
consisting of several, related features that we'll use to build our application.
When we need something from a module or library, we import it.
Here we import the `Component` decorator from the Angular 2 **_core_** library
that we'll use as a decorator (`@Component`) to attach metadata to our component class.
.
+makeExcerpt('src/app/cli-quickstart.component.ts', 'import')
h3#component-decorator @Component decorator
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`Component` is a *decorator* function that associates Angular *metadata* with a
component class.
The metadata tell Angular how to create and display instances of this component.
We apply this function to the component class by prefixing the function name with the
**@** symbol and invoking it with a metadata object, just above the class.
+makeExcerpt('src/app/cli-quickstart.component.ts', 'metadata')
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This particular metadata object has four fields, a `moduleId`, a `selector` a `templateUrl` and an array of `styleUrls`.
The **moduleId** specifies the location of _this_ component definition file
so that Angular can find the corresponding _template_ and _style_ files with URLs that
are relative to this component file.
The module loader sets the value of `module.id` at runtime;
we're using that value to set the metadata `moduleId` property.
The **selector** is a [CSS selector](https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Getting_Started/Selectors)
identifying the HTML element that represents this component.
The element tag name for this component is `cli-quickstart-app`.
Angular creates and displays an instance of our `CliQuickstartAppComponent`
wherever it encounters a `<cli-quickstart-app>` element in the host HTML.
The **templateUrl** locates the component's companion template HTML file.
The template tells Angular how to render this component's view.
Our template is a single `<h1>` element surrounding some peculiar Angular data binding syntax.
+makeExample('src/app/cli-quickstart.component.html', null, 'src/app/cli-quickstart.component.html')(format='.')
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The `{{title}}` is an _interpolation_ binding that causes Angular to display the component's
`title` property. After out edit, Angular displays _My First Angular 2 App_.
We'll learn more about data binding as we read through the documentation.
The **styleUrls** array specifies the location(s) of the component's private CSS style file(s).
The CLI generated an empty file for us and we added styles to it.
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### Component class
At the bottom of the component definition file is the component class named `CliQuickstartAppComponent`.
+makeExcerpt('cli-quickstart/ts/src/app/cli-quickstart.component.ts', 'class')
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This class contains the `title` property that we're displaying in our template.
We can expand this class with more properties and application logic.
We **export** `CliQuickstartAppComponent` so that we can **import** it elsewhere in our application ... as we're about to do.
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### The *main.ts* file
How does Angular know what to do with our component? We have to tell it.
We _bootstrap_ our application in the file `main.ts`.
+makeExcerpt('src/main.ts', 'important')
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We import the two things we need to launch the application:
1. Angular's browser `bootstrap` function
1. The application root component, `CliQuickstartAppComponent`.
Then we call `bootstrap` with `CliQuickstartAppComponent`.
### Bootstrapping is platform-specific
Notice that we import the `bootstrap` function from `@angular/platform-browser-dynamic`,
not `@angular/core`.
Bootstrapping isn't core because there isn't a single way to bootstrap the app.
True, most applications that run in a browser call the bootstrap function from
this library.
But it is possible to load a component in a different environment.
We might load it on a mobile device with [Apache Cordova](https://cordova.apache.org/) or [NativeScript](https://www.nativescript.org/).
We might wish to render the first page of our application on the server
to improve launch performance or facilitate
[SEO](http://www.google.com/webmasters/docs/search-engine-optimization-starter-guide.pdf).
These targets require a different kind of bootstrap function that we'd import from a different library.
### Why create a *main.ts* file?
Both `main.ts` and the application component files are tiny.
This is just a QuickStart.
We could have merged these two files into one
and spared ourselves some complexity.
We'd rather demonstrate the proper way to structure an Angular application.
App bootstrapping is a separate concern from presenting a view.
Mixing concerns creates difficulties down the road.
We might launch the `CliQuickstartAppComponent` in multiple environments with different bootstrappers.
Testing the component is much easier if it doesn't also try to run the entire application.
Let's make the small extra effort to do it *the right way*.
### Loading the application with SystemJS
The CLI uses `System.js` to load the application. We just need to call `System.import` and pass it our `main.ts`
file to boot our application.
+makeExcerpt('src/index.html', 'import')
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### Displaying the root component
When Angular calls the `bootstrap` function in `main.ts`, it reads the `CliQuickstartAppComponent`
metadata, finds the `cli-quickstart-app` selector, locates an element tag named `cli-quickstart-app`
in the `<body>` tag of the `index.html`, and renders our application's view between those tags.
+makeExcerpt('src/index.html', 'body')
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This is just a taste of Angular 2 develoment. There's much more to learn. Now really is the time to
head over to the [Tour of Heroes Tutorial](./tutorial)!