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

@Component({
  selector: 'app-root',
  // templateUrl: './app.component.html',
  template:`
      <div *ngFor="let v of getArray();">
        {{v}}
      </div>
  `,
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  getArray(){
    console.log("getArray");
    return [1,2,3,5,6];
  }
}

上記を実行するとlogに
11:17:30.567 app.component.ts:15 getArray
11:17:30.578 app.component.ts:15 getArray
11:17:30.579 lang.js:130 Angular is running in the development mode. Call enableProdMode() to enable the production mode.
11:17:30.581 app.component.ts:15 getArray
11:17:30.582 app.component.ts:15 getArray

と表示されます。なぜ4回も実行されるのでしょうか?