First Angular app lesson 1 - Hello world-Toy模板网

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Before you start

This lesson starts from a pre-built app that will serve as a baseline for the application you'll be building in this tutorial. We've provided starter code so you can:

Start with the code example for the beginning of this lesson. Choose from the live example / download example to:
- Use the live example in StackBlitz, where the StackBlitz interface is your IDE.
- Use the download example and unzip it into a directory named: first-app. Open that directory in your IDE.

If you haven't reviewed the introduction, visit the tutorial overview page to make sure you have everything you need to complete this lesson.

If you have any trouble during this lesson, you can review the completed code for this lesson, in the live example / download example for this lesson.

After you finish

The updated app you have after this lesson confirms that you and your IDE are ready to begin creating an Angular app.

Lesson steps

Perform these steps on the app code in your chosen IDE (locally or using the StackBlitz).

Step 1 - Test the default app

In this step, after you download the default starting app, you build the default Angular app. This confirms that your development environment has what you need to continue the tutorial.

In the Terminal pane of your IDE:

In your project directory, navigate to the first-app directory.
Run this command to install the dependencies needed to run the app.
```
content_copynpm install
```
Run this command to build and serve the default app.
```
content_copyng serve
```
The app should build without errors.
In a web browser on your development computer, open http://localhost:4200.
Confirm that the default web site appears in the browser.
You can leave ng serve running for as you complete the next steps.

Step 2 - Review the files in the project

In this step, you get to know the files that make up a default Angular app.

In the Explorer pane of your IDE:

In your project directory, navigate to the first-app directory.
Open the src directory to see these files.
1. In the file explorer, find the Angular app files (/src).
  1. index.html is the app's top level HTML template.
  2. style.css is the app's top level style sheet.
  3. main.ts is where the app start running.
  4. favicon.ico is the app's icon, just as you would find in web site.
2. In the file explorer, find the Angular app's component files (/app).
  1. app.component.ts is the source file that describes the app-root component. This is the top-level Angular component in the app. A component is the basic building block of an Angular application. The component description includes the component's code, HTML template, and styles, which can be described in this file, or in separate files.
    
    In this app, the styles are in a separate file while the component's code and HTML template are in this file.
  2. app.component.css is the style sheet for this component.
  3. New components are added to this directory.
3. In the file explorer, find the image directory (/assets) contains images used by the app.
4. In the file explorer, find the support files are files and directories that an Angular app needs to build and run, but they are not files that you normally interact with.
  1. .angular has files required to build the Angular app.
  2. .e2e has files used to test the app.
  3. .node_modules has the node.js packages that the app uses.
  4. angular.json describes the Angular app to the app building tools.
  5. package.json is used by npm (the node package manager) to run the finished app.
  6. tsconfig.* are the files that describe the app's configuration to the TypeScript compiler.

After you have reviewed the files that make up an Angular app project, continue to the next step.

Step 3 - Create Hello World

In this step, you update the Angular project files to change the displayed content.

In your IDE:

Open first-app/src/index.html.
In index.html, replace the <title> element with this code to update the title of the app.

Replace in src/index.html
```
content_copy<title>Homes</title>
```
Then, save the changes you just made to index.html.
Next, open first-app/src/app/app.component.ts.
In app.component.ts, in the @Component definition, replace the template line with this code to change the text in the app component.

Replace in src/app/app.component.ts
```
content_copytemplate: `<h1>Hello world!</h1>`,
```
In app.component.ts, in the AppComponent class definition, replace the title line with this code to change the component title.

Replace in src/app/app.component.ts
```
content_copytitle = 'homes';
```
Then, save the changes you made to app.component.ts.
If you stopped the ng serve command from step 1, in the Terminal window of your IDE, run ng serveagain.
Open your browser and navigate to localhost:4200 and confirm that the app builds without error and displays Hello world in the title and body of your app: