`signal()`

Creates a writable reactive value that notifies consumers when it changes.

Since Angular 16+ Spec ↗

Syntax

signal<T>(initialValue: T, options?): WritableSignal<T>

Parameters

Name	Type	Required	Description
`initialValue`	`T`	No	The initial value held by the signal.
`options`	`object`	No	Optional config; supports an equal comparator function.

Returns

WritableSignal<T> — A getter function with set(), update(), and asReadonly() methods.

Examples

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

@Component({
  selector: 'app-counter',
  standalone: true,
  template: `<button (click)="inc()">{{ count() }}</button>`,
})
export class CounterComponent {
  count = signal(0);
  inc() {
    this.count.update((n) => n + 1);
  }
}

const user = signal({ name: 'Ada' });
user.set({ name: 'Grace' });
console.log(user().name);

Notes

Read a signal by calling it as a function: `count()`. Use `set()` to replace the value and `update()` to derive the next value from the current one. Reading inside a template or computed/effect creates a reactive dependency. Use the `equal` option to skip notifications for values you consider equal.