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How does an Angular application work

How does an Angular application work

Every Angular app consists of a file named angular.json. This file will contain all the configurations of the app. While building the app, the builder looks at this file to find the entry point of the application. Following is an image of the angular.json file: 

    
      "build": {
        "builder": "@angular-devkit/build-angular:browser",
        "options": {
          "outputPath": "dist/angular-starter",
          "index": "src/index.html",
          "main": "src/main.ts",
          "polyfills": "src/polyfills.ts",
          "tsConfig": "tsconfig.app.json",
          "aot": false,
          "assets": [
            "src/favicon.ico",
            "src/assets"
          ],
          "styles": [
            "./node_modules/@angular/material/prebuilt-themes/deeppurple-amber.css",
            "src/style.css"
          ]
        }
      }

Inside the build section, the main property of the options object defines the entry point of the application which in this case is main.ts. 
The main.ts file creates a browser environment for the application to run, and, along with this, it also calls a function called bootstrapModule, which bootstraps the application. These two steps are performed in the following order inside the main.ts file: 

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';


platformBrowserDynamic().bootstrapModule(AppModule)

In the above line of code, AppModule is getting bootstrapped. 
The AppModule is declared in the app.module.ts file. This module contains declarations of all the components. 
Below is an example of app.module.ts file:

    
      import { BrowserModule } from '@angular/platform-browser';
      import { NgModule } from '@angular/core';
      import { AppComponent } from './app.component';

      @NgModule({
        declarations: [
          AppComponent
        ],
        imports: [
          BrowserModule
        ],
        providers: [],
        entryComponents: [],
        bootstrap: [AppComponent]
      })
      export class AppModule { }

As one can see in the above file, AppComponent is getting bootstrapped. 
This component is defined in app.component.ts file. This file interacts with the webpage and serves data to it. 
Below is an example of app.component.ts file:

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

      @Component({
        selector: 'app-root',
        templateUrl: './app.component.html',
        styleUrls: ['./app.component.css']
      })
      export class AppComponent {
        title = 'angular';
      }

Each component is declared with three properties:
1. Selector - used for accessing the component
2. Template/TemplateURL - contains HTML of the component 
3. StylesURL - contains component-specific stylesheets 

After this, Angular calls the index.html file. This file consequently calls the root component that is app-root. The root component is defined in app.component.ts. 
This is how the index.html file looks: 

    
      <!doctype html>
      <html lang="en">
      <head>
        <meta charset="utf-8">
        <title>Angular</title>
        <base href="/">
        <meta name="viewport" content="width=device-width, initial-scale=1">
      </head>
      <body>
        <app-root></app-root>
      </body>
      </html>

The HTML template of the root component is displayed inside the <app-root> tags. 

This is how every angular application works.


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