Fix Infinite Loops in Angular Effects

Angular effects run continuously when they read a signal and write back to the same/dependent signal, causing infinite re-execution. Each effect run reads signals → triggers signal change → effect re-runs → 100% CPU crash.

Solutions:

Guard condition prevents unnecessary runs
allowSignalWrites: true + careful logic
Use computed() for derivations instead

Code Example:

Code

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

@Component({
  template: `<input [(model)]="name" (input)="markDirty()">
             <p>Status: {{ status() }}</p>`
})
export class UserProfile {
  name = signal('John');
  isDirty = signal(false);
  status = signal('synced');
  
  //  INFINITE LOOP
  badEffect = effect(() => {
    this.status.set(`Saving ${this.name()}`); // Triggers re-run!
  });
  
  //  PROPER FIX: Guard condition
  constructor() {
    effect(() => {
      if (this.isDirty()) {
        this.status.set(`Saving ${this.name()}`);
        // API call here...
        this.isDirty.set(false);
        this.status.set('Saved');
      }
    });
  }
  
  markDirty() {
    this.isDirty.set(true);  // Triggers effect once
  }
}

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How do Angular effects create infinite loops and what's the proper fix?

Solutions:

Guard condition prevents unnecessary runs
allowSignalWrites: true + careful logic
Use computed() for derivations instead

Code Example:

Code

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

@Component({
  template: `<input [(model)]="name" (input)="markDirty()">
             <p>Status: {{ status() }}</p>`
})
export class UserProfile {
  name = signal('John');
  isDirty = signal(false);
  status = signal('synced');
  
  //  INFINITE LOOP
  badEffect = effect(() => {
    this.status.set(`Saving ${this.name()}`); // Triggers re-run!
  });
  
  //  PROPER FIX: Guard condition
  constructor() {
    effect(() => {
      if (this.isDirty()) {
        this.status.set(`Saving ${this.name()}`);
        // API call here...
        this.isDirty.set(false);
        this.status.set('Saved');
      }
    });
  }
  
  markDirty() {
    this.isDirty.set(true);  // Triggers effect once
  }
}

How do Angular effects create infinite loops and what's the proper fix?

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