The package.json file 

The package.json file is very common in web applications that use Node.js modules. It is often found in frontend applications nowadays, in addition to server-side applications with Node.js. With the Angular framework, it is not different; this is one of the great advantages of the new version of Angular, since we can only import modules that are extremely necessary for the application, reducing the size and build time. Let's look at the contents of the package.json file. We added some comments before each important section:

{
"name": "chapter03",
"version": "0.0.0",
"license": "MIT",
// Npm commands, based on Angular/Cli commands, including: test and     build.
"scripts": {
"ng": "ng",
"start": "ng serve",
"build": "ng build --prod",
"test": "ng test",
"lint": "ng lint",
"e2e": "ng e2e"
 },
"private": true,
// Dependencies to work in production, including:
@angular/core, @angular/common, @angular/route and many more.
"dependencies":{
...
},
// Dependencies only in development environment, including modules for test, TypeScript version, Angular/Cli installed locally and others.
"devDependencies": {
...
}
} 

This file is automatically changed when we install a new module. And, we often add some commands inside the tag scripts, as you will see in the next chapters. You can read more about the package.json file in the official npm documentation at https://docs.npmjs.com/files/package.json.