当我在项目中更改状态时，此状态应标记为更改Angular 4的日期

Question

我有Project的接口，进入这个变量状态声明为数字。但是，当状态发生变化时，如何为每次更改添加日期。

这是界面

export interface Project {
state: number;
}

这是我编辑项目的时候

 <div fxLayout="column" fxLayoutAlign="start start" fxLayoutGap="15px">
      <app-dropdown [(ngModel)]="editProject.state" label="Project State" labelWidth="100px" optionWidth="250px" orientation="top"
        [items]="projectState" (click)="changeStatesAndTypes()"></app-dropdown>
    </div>

这是changeStateAndTypes方法。

changeStatesAndTypes() {
  if (this.editProject.type === 2) {
      this.projectState = [{key: 0, value: 'Published'}];
      this.editProject.state = 0;
  }  if (this.editProject.state === 0) {
    this.projectType =
     [{key: 0, value: 'Approved'},
     {key: 1, value: 'Denied'},
     {key: 2, value: 'Waiting for Approval'},
     {key: 4, value: 'ReDo'}];
  }  if (this.editProject.type === 0) {
    this.projectState = [{key: 2, value: 'In progress'}];
    this.editProject.state = 2;
  }
 }