by use keyup event in angular not working code example

Example: how to bind the value of keyup event in runtime to a variable

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

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

       sampleString: string;

       updateBox(e) {
         this.sampleString = e.target.value; 
       }

    }



  
{{box.value}}
This is sampleString Value: {{sampleString}}