1.双向数据绑定

1-1app.modult.ts中配置

//1.在app.module.ts根目录中导入并注册
import {FormsModule} from '@angular/forms'
@NgModule({
 ...
  imports: [
    ...
    FormsModule    //注册
  ],
 ...
})

1-2在组件中使用

//.component.ts
 export class HeaderComponent implements OnInit {
  public msg:string='hello world';
    ...
  }
}
//.html
<input type="text" [(ngModel)]="msg">       // [(ngModel)]="msg"   快捷键ng就可以出来