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What is effect() in Angular?

AngularJunior~1 min read

effect() is a way to react to signal changes. When a signal changes, the code inside effect() runs automatically.

Example:

ts

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

const counter = signal(0);

effect(() => {
  console.log('New value:', counter());
});

If you call counter.set(5), the console will show New value: 5.

Why it is needed

effect() is used for side effects that are not directly tied to the template:

logging,
server requests,
writing data to localStorage,
updating the DOM outside Angular.

The main point:

effect() tracks on its own which signals it reads;
it re-runs the code when they change;
it returns nothing, it simply reacts.

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