typed-changes.component.ts

import { Component, Input, OnChanges, SimpleChanges, SimpleChange } from '@angular/core';

declare class TypedChange<T = any> extends SimpleChange {
  previousValue: T;
  currentValue: T;
  firstChange: boolean;
  constructor(previousValue: T, currentValue: T, firstChange: boolean);
  /**
   * Check whether the new value is the first value assigned.
   */
  isFirstChange(): boolean;
}


interface MyChanges extends SimpleChanges {
  status: TypedChange<string>
}

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent implements OnChanges {
  @Input() status: string;

  name = 'Angular 5';

  ngOnChanges( changes: MyChanges ) {
    if( changes.status ) {
      console.log(changes.status.currentValue.substr(0));
    }
  }
}