Change the Color of the TextBox Based on its Value in Angular TextBox component

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

@Component({
    selector: 'app-root',
    template: `<div class="wrap">
                <label> Normal Input </label>
                <div class="e-input-group">
                    <input class="e-input" type="text" (focus)="focusIn($event.target)"
                    placeholder = "Enter numeric values" (blur)="focusOut($event.target)" (keyup)="onKeyup($event)"/>
                </div>
                 <label> Floating Input </label>
                <div class="e-float-input">
                    <input type="text"(focus)="focusIn($event.target)" (blur)="focusOut($event.target)" (keyup)="onKeyup($event)" required/>
                    <span class="e-float-line"></span>
                    <label class="e-float-text">Enter numeric values</label>
                </div>
              </div>`
})

export class AppComponent {
    public focusIn(target: HTMLElement): void {
        target.parentElement.classList.add('e-input-focus');
    }

    public focusOut(target: HTMLElement): void {
        target.parentElement.classList.remove('e-input-focus');
    }
    public onKeyup(event): void {
    let str = event.target.value.match(/^[0-9]+$/);
    if (!((str && str.length > 0)) && event.target.value.length) {
       event.target.parentElement.classList.add('e-error');
    } else {
      event.target.parentElement.classList.remove('e-error');
    }
  }
}

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { FormsModule } from '@angular/forms';
/**
 * Module
 */
@NgModule({
    imports: [
        BrowserModule,
        FormsModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);