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What are Angular Signals?

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01

Understand the problem

Explain the modern signals reactivity model.

signalsreactivity
02

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03

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Signals are a fine-grained reactivity primitive: signal() holds a value, computed() derives from signals, and effect() runs side effects when dependencies change. They enable precise, zoneless change detection — Angular re-renders only what actually depends on a changed signal, rather than checking the whole

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04

Read the code

signal, computed, effect
import { Component, signal, computed, effect } from '@angular/core';

@Component({
  selector: 'app-root',
  standalone: true,
  template: '<button (click)="inc()">count {{ count() }} → doubled {{ doubled() }}</button>',
})
export class AppComponent {
  count = signal(0);
  doubled = computed(() => this.count() * 2);   // derived + memoized

  constructor() {
    effect(() => console.log('count is', this.count())); // reacts to changes
  }
  inc() { this.count.update(c => c + 1); }
}
05

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