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Angular 9 Coding Style Guideline - 8, 7, 6, 5, 4, 2

The Angular coding guideline will helps us to understand to write the great code. It must be follows each and every Angular developers.

Explore -  What Are Differences in Angular 9, 8, 7, 6, 5, 4, 2?

Single Responsibility -
Apply the single responsibility principle (SRP) to all components, services, and other symbols. This helps make the app cleaner, easier to read and maintain, and more testable.

Rule of One - Do define one thing, such as a service or component, per file and consider limiting files to 400 lines of code.

Small functions - Do define small functions and consider limiting to no more than 75 lines.
General Naming Guidelines -
Do use consistent names for all symbols and the recommended pattern is - feature.type.ts.

Separate file names with dots and dashes -
1.      Do use dashes to separate words in the descriptive name.
2.      Do use dots to separate the descriptive name from the type.
3.      Do use consistent type names for all components following a pattern that describes the component's feature then its type. A recommended pattern is feature.type.ts.
4.      Do use conventional type names including .service, .component, .pipe, .module, and .directive. Invent additional type names if you must but take care not to create too many.
Example - users.service.ts | users.pipe.ts |users.module.ts
Note - don't user short form like - srv, .svc, .srve. It is very confusing.

Symbols and file names -
1.      Do use consistent names for all assets named after what they represent.
2.      Do use upper camel case for class names.
3.      Do match the name of the symbol to the name of the file.
4.      Do append the symbol name with the conventional suffix (such as Component, Directive, Module, Pipe, or Service) for a thing of that type.
5.      Do give the filename the conventional suffix (such as .component.ts, .directive.ts, .module.ts, .pipe.ts, or .service.ts) for a file of that type.

Symbol Name, do like this - 
@Component({ ... })
export class UsersComponent { }

OR   

@Component({ ... })
export class UserDetailComponent { }

OR

@Pipe({ name: 'initCaps' })
export class InitCapsPipe implements PipeTransform { }

OR

@Injectable()
export class UserProfileService { }

File Name, do like this -
users.component.ts

OR

user-detail.component.ts

OR

init-caps.pipe.ts

OR

user-profile.service.ts

Bootstrapping -
1.      Do put bootstrapping and platform logic for the app in a file named main.ts.
2.      Do include error handling in the bootstrapping logic.
3.      Avoid putting app logic in main.ts. Instead, consider placing it in a component or service.
Example -

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { AppModule }              from './app/app.module';
platformBrowserDynamic().bootstrapModule(AppModule)
  .then(success => console.log(`Bootstrap success`))
  .catch(err => console.error(err));

Component Selectors -
Do use dashed-case or kebab-case for naming the element selectors of components.
Example - The prefix toh represents Tour of Users

Do like this -
@Component({
  selector: 'toh-user-button',
  templateUrl: './user-button.component.html'
})
export class UserButtonComponent {}

Avoid using like this -
@Component({
  selector: 'tohuserButton',
  templateUrl: './user-button.component.html'
})
export class UserButtonComponent {}

Component custom prefix -
1.      Do use a hyphenated, lowercase element selector value; for example, admin-users.
2.      Do use a custom prefix for a component selector.
3.      Do use a prefix that identifies the feature area or the app itself.

Example - Do like this,
@Component({
  selector: 'admin-users'
})
export class UsersComponent {}

And avoid like this,
// UsersComponent is in an Admin feature
@Component({
  selector: 'users'
})
export class UsersComponent {}

Directive custom prefix -
1.      Do use a custom prefix for the selector of directives (e.g, the prefix toh from Tour of Users).
2.      Do spell non-element selectors in lower camel case unless the selector is meant to match a native HTML attribute.

Example, Do like this,
/* Do this */
@Directive({
  selector: '[tohValidate]'
})
export class ValidateDirective {}

And avoid like this,
/* avoid */
@Directive({
  selector: '[validate]'
})
export class ValidateDirective {}

Pipe names -
Do use consistent names for all pipes, named after their feature. The pipe class name should use UpperCamelCase and the corresponding name string should use lowerCamelCase. The name string cannot use hyphens ("dash-case" or "kebab-case")

Symbol Name -
@Pipe({ name: 'ellipsis' })
export class EllipsisPipe implements PipeTransform { }

OR  
@Pipe({ name: 'initCaps' })
export class InitCapsPipe implements PipeTransform { }

File Name -
ellipsis.pipe.ts

OR

init-caps.pipe.ts

Unit test file names -
1.      Do name test specifications file the same as the component they test.
2.      Do name test specification files with a suffix of .spec.

For example,
Components/ users.component.spec.ts/ user-detail.component.spec.ts
Services/  user.service.spec.ts/ logger.service.spec.ts
Pipes/  ellipsis.pipe.spec.ts/ init-caps.pipe.spec.ts

End-to-End (E2E) test file names -
Do name end-to-end test specification files after the feature they test with a suffix of .e2e-spec.

Example,
End-to-End Tests/  app.e2e-spec.ts/ users.e2e-spec.ts

Angular NgModule names -
Do append the symbol name with the suffix Module.
Do give the file name the .module.ts extension.
Do name the module after the feature and folder it resides in.

Examples,

Symbol Name -    
@NgModule({ ... })
export class AppModule { }

OR

@NgModule({ ... })
export class HeroesModule { }

OR

@NgModule({ ... })
export class AppRoutingModule { }

File Name -
app.module.ts

OR
users.module.ts

OR
app-routing.module.ts

By Anil Singh | Rating of this article (*****)

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