computed()

Creates a computed signal.

Example

const name = atom('name', 'John')
const greeting = computed('greeting', () => `Hello ${name.value}!`)
console.log(greeting.value) // 'Hello John!'

computed may also be used as a decorator for creating computed class properties.

Example

class Counter {
  max = 100
  count = atom<number>(0)

  @computed get remaining() {
    return this.max - this.count.value
  }
}

You may optionally pass in a ComputedOptions when used as a decorator:

Example

class Counter {
  max = 100
  count = atom<number>(0)

  @computed({isEqual: (a, b) => a === b})
  get remaining() {
    return this.max - this.count.value
  }
}

Signature

computed<Value, Diff>(name: string, compute: Function, options?: ComputedOptions<Value, Diff>): Computed<Value, Diff>;

Type parameters

• Value
• Diff = unknown

Parameters

Name	Type	Description
name	string	The name of the signal.
compute	(previousValue: typeof UNINITIALIZED | Value, lastComputedEpoch: number) => Value | WithDiff<Value, Diff>	The function that computes the value of the signal.
options?	ComputedOptions<Value, Diff>	Options for the signal.

Returns

Computed<Value, Diff>

Defined in: signia/src/Computed.ts:342

Signature

computed(target: any, key: string, descriptor: PropertyDescriptor): PropertyDescriptor;

Parameters

Name	Type
target	any
key	string
descriptor	PropertyDescriptor

Returns

PropertyDescriptor

Defined in: signia/src/Computed.ts:352

Signature

computed<Value, Diff>(options?: ComputedOptions<Value, Diff>): Function;

Type parameters

• Value
• Diff = unknown

Parameters

Name	Type
options?	ComputedOptions<Value, Diff>

Returns

Function

Signature

(target: any, key: string, descriptor: PropertyDescriptor): PropertyDescriptor;

Parameters

Name	Type
target	any
key	string
descriptor	PropertyDescriptor

Returns

PropertyDescriptor

Defined in: signia/src/Computed.ts:358