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What is a directive and what are the types?

Q: What is a directive and what are the types?

**Core concept.** A directive attaches **behaviour** to elements in the DOM. There are three kinds: **components** (directives *with* a template), **structural** directives that change layout by adding/removing elements ( *ngIf , *ngFor — note the * ), and **attribute** directives that change an element's appearance or behaviour ( ngClass , ngStyle , or your own). Component directive with a template Structur

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A custom attribute directive

import { Directive, ElementRef, HostListener, Input } from '@angular/core';

@Directive({ selector: '[appHighlight]', standalone: true })
export class HighlightDirective {
  @Input() appHighlight = 'yellow';        // configurable via attribute

  constructor(private el: ElementRef) {}

  @HostListener('mouseenter') onEnter() {
    this.el.nativeElement.style.background = this.appHighlight;
  }
  @HostListener('mouseleave') onLeave() {
    this.el.nativeElement.style.background = '';
  }
}

// Usage:  <p appHighlight="lightblue">Hover me</p>

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