ngOnInit()

This is the documentation for Angular 6.
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A callback method that is invoked immediately after the default change detector has checked the directive's data-bound properties for the first time, and before any of the view or content children have been checked. It is invoked only once when the directive is instantiated.

ngOnInit(): void

Example

The following snippet shows how a component can implement this interface to define its own initialization method.

@Component({selector: 'my-cmp', template: `...`})
class MyComponent implements OnInit {
  ngOnInit() {
    // ...
  }
}