Command-line Interface – Angular


Command-line Interface

Motivation

Angular is closely associated with its command-line interface (CLI). The CLI streamlines generation of the Angular file system. It deals with most of the configuration behind the scenes so developers can start coding. The CLI also has a low learning curve recommendable for any newcomer wanting to jump right in. Heck, even experienced Angular developers rely on the CLI!

Installation

The Angular CLI requires Node.js and Node Package Manager (NPM). You can check for these programs with the terminal command: node -v; npm -v. Once installed, open a terminal and install the Angular CLI with this command: npm install -g @angular/cli or npm install -g @angular/[email protected] to install the latest version of angular cli. This can be executed from anywhere on your system. The CLI is configured for global use with the -g flag.

Verify the CLI is there with the command: ng -v. This outputs several lines of information about the angular cli installed in your machine. One of these lines state the version of the installed CLI.

Recognize that ng is the basic building block of the CLI. All your commands will begin with ng. Time to take a look at four of the most common commands prefixed with ng.

Key Commands

  • ng new
  • ng serve
  • ng generate
  • ng build
  • ng update
  • ng add (Angular 6)

The key terms for each of these are quite telling. Together, they comprise what you will need to hit the ground running with Angular. Of course, there are many more. All commands are outlined in the CLI’s GitHub Documentation1. You will likely find that the commands listed above will cover the necessary bases.

ng new

ng new creates a new Angular file system. This is a surreal process. Please navigate to a file location desirable for new application generation. Type this command as follows, replacing [name-of-app] with whatever you want: ng new [name-of-app]. For Example ng new myapp here myapp the name which I’ve given to my app. Which will generate your app with a default folder structure. There wil be a lot of generated files, Don’t consider every file. You’ll be mostly working with the src folder.

But Feel free to explore other files within. Try to not make any changes yet. All of what you need to run your first Angular application comes packaged together in this generated file system.

ng serve

To get the application running, the ng serve command must execute within the [name-of-app] folder. Anywhere within the folder will do. The Angular CLI must recognize that it is within an environment generated with ng new. It will run provided this one condition. Go ahead and try it: ng serve.

The application runs on port 4200 by default. You can view the Angular application by navigating to localhost:4200 in any web browser. Angular works across all browsers. Unless you are using an old version of Internet Explorer, the application will pop up. It displays the official Angular logo alongside a list of helpful links.

Ok, the application runs. It hopefully functions, but you need to know what is going on under the hood. Refer back to the [name-of-app] file system. Navigate [name-of-app] -> src -> app. Therein lies the files responsible for what you saw on localhost:4200.

Okay, What if you are running 2 Angular app which runs on PORT 4200 by default or let me say that the PORT 4200 has been busy? You can change your default PORT by using a cli commang ng serve --port 4000 here 4000 is the PORT that I want to run. You can change it to a PORT that ypu wnat to run your app.

ng generate

The .component files define an Angular component including its logic (.ts), style (.css), layout (.html), and testing (.spec.ts). The app.module.ts particularly stands out. Together, these two groups of files work together as component and module. Both component and module are two separate examples of Angular schematics. Schematics classify the different purpose-driven blocks of code generatable with ng generate.

For the sake of this article, understand that a module exports and imports assets to and from an underlying component tree. A component concerns itself with one section of the user interface. That unit’s logic, style, layout, and testing stays encapsulated within the various .component files.

As for ng generate, this command can generate skeletons for each of the available Angular schematics2. Navigate to [name-of-app -> src -> app]. Try generating a new component by executing: ng generate component [name-of-component]. Replace [name-of-component] with whatever you would like. A new file [name-of-component] will pop up along with its necessary component files.

You can see that ng generateexpedites Angular’s boilerplate code. ng generate also wires things up. Schematics created within context of an Angular file system connect with the system’s root module. In this case, that would be app.module.ts file inside [name-of-app -> src -> app].

ng build

The ng serve command runs the project using lite-server webserver installed with other dependencies during the the creation of project with ng new. If you want to serve your Angular web application with your own webserver like Apache or Nginx, then you will have to build all the source TypeScript files with ng build.

ng build produces a development build with all source maps, JavaScript files, CSS and HTML files and puts it in the [name-of-app] -> dist directory. This directory contains the index.html file which is the entry point to the Angular application. The content of this folder can be directly put into the web root of any web server to deploy. You don’t need ng serve anymore.

The path where all the built files are kept is defined with the path string given in outputPath key in [name-of-app] -> angular.json. By default it is "outputPath": "dist".

Note that a simple build with ng build is not optimized for production run. That means that the JavaScript and CSS is not minified, it may still contain some dead code and it has a huge size due to JIT compilation.

For a production ready build, use ng build --prod. The --prod option enables minification and uglification. It also compiles with Ahead-of-Time compilation strategy which is very fast for use in production. All the libraries used are concatenated into a few files. This build can be run in production servers.

ng update

In angular cli ng update do automatic updation on all the angular and npm packages to latest versions.

Here is the syntax and options can be used with ng update.

ng update [package]

ng add

ng add will use npm to download new dependencies and invoke an installation script.

ng add <package>

Options

  • dry-run
    --dry-run (alias: -d) Run through without making any changes.
  • force
    --force If false, will error out if installed packages are incompatible with the update.
  • all
    --all Whether to update all packages in package.json.
  • next
    --next Use the largest version, including beta and RCs.
  • migrate-only
    --migrate-only Only perform a migration, does not update the installed version.
  • from
    --from Version from which to migrate from. Only available with a single package being updated, and only on migration only.
  • to
    --to Version up to which to apply migrations. Only available with a single package being updated, and only on migrations only. Requires from to be specified. Default to the installed version detected.
  • registry
    --registry The NPM registry to use.
  • style
    --style The file extension to be used for style files. (Ex. ng new app –style=scss)

Conclusion

These commands fulfill the basics. Angular’s CLI is an incredible convenience that expedites application generation, configuration, and expansion. It does all this while maintaining flexibility, allowing the developer to make necessary changes.

Please check out those links on localhost:4200 if you have not already. Do not forget to run ng serve before opening it up. With a better understanding of the CLI, you are now ready to learn more about what is generated by its most essential commands.

Sources

  1. Google. “angular/angular-cli/wiki#additional-commands.” GitHub.
  2. Google. “angular/angular-cli/wiki/generate#available-schematics.” GitHub.

Resources

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