View Encapsulation

View encapsulation defines whether the template and styles defined within the component can affect the whole application or vice versa. Angular provides three encapsulation strategies:

• Emulated (default) - styles from main HTML propagate to the component. Styles defined in this component's @Component decorator are scoped to this component only.
• Native - styles from main HTML do not propagate to the component. Styles defined in thiscomponent's @Component decorator are scoped to this component only.
• None - styles from the component propagate back to the main HTML and therefore are visible to all components on the page. Be careful with apps that have None and Native components in the application. All components with None encapsulation will have their styles duplicated in all components with Native encapsulation.

@Component({
// …
encapsulation: ViewEncapsulation.None,
styles: [
// …
]
})
export class HelloComponent {
// …
}

View Example

原文: https://angular-2-training-book.rangle.io/handout/advanced-components/view_encapsulation.html