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What is the effect() function in Angular Signals, and when should you NOT use it?

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01

Understand the problem

Explain signals-based side effects and their limitations.

signalsreactivity
02

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03

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An effect() runs side-effects dynamically when one or more signals inside it change. It is designed for logging, synchronizing with custom DOM elements, or analytics. It should not be used to set other signals (which can cause infinite loop dependencies) or perform logic better suited for computed().

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04

Read the code

Proper use of an effect to synchronize state to LocalStorage
import { Component, signal, effect } from '@angular/core';

@Component({
  selector: 'app-theme-selector',
  standalone: true,
  template: '<button (click)="toggleTheme()">Toggle Theme: {{ theme() }}</button>'
})
export class ThemeSelectorComponent {
  theme = signal('light');

  constructor() {
    effect(() => {
      localStorage.setItem('user-theme', this.theme());
    });
  }

  toggleTheme() {
    this.theme.update(t => t === 'light' ? 'dark' : 'light');
  }
}
05

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