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main.ts

index.html

import { bootstrapApplication } from '@angular/platform-browser';
import { Component, Directive, Input, HostBinding, HostListener } from '@angular/core';
import { CommonModule } from '@angular/common';

@Directive({
  selector: '[w3Highlight]',
  standalone: true
})
export class HighlightDirective {
  @Input('w3Highlight') highlightColor = 'yellow';
  @HostBinding('style.transition') transition = 'background-color 150ms ease-in-out';
  @HostBinding('style.backgroundColor') bg = '';

  @HostListener('mouseenter') onEnter() { this.bg = this.highlightColor; }
  @HostListener('mouseleave') onLeave() { this.bg = ''; }
}

@Component({
  selector: 'app-root',
  standalone: true,
  imports: [CommonModule, HighlightDirective],
  styles: [`
    .box { padding: 10px; border: 1px dashed #bbb; border-radius: 6px; }
    .row { display: flex; gap: 12px; align-items: center; flex-wrap: wrap; }
    input { padding: 6px 8px; }
  `],
  template: `
    <h3>Attribute Directive (highlight)</h3>

    <div class="row">
      <label>Color: <input [value]="color" (input)="color = $any($event.target).value" placeholder="e.g. lightyellow"></label>
      <button (click)="toggle()">{{ enabled ? 'Disable' : 'Enable' }}</button>
    </div>

    <p style="margin-top:10px">Hover the boxes to see the effect:</p>

    <div class="box" [w3Highlight]="color" *ngIf="enabled">I get highlighted on hover</div>
    <div class="box">I do not</div>
  `
})
export class App {
  color = 'lightyellow';
  enabled = true;
  toggle() { this.enabled = !this.enabled; }
}

bootstrapApplication(App);

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Angular Directives - Attribute Directive</title>
</head>
<body>
  <app-root></app-root>
</body>
</html>