Skip to main content

let$$

Types​

function let$$<GValue>(
  ...initialValue: ICreateReplayLastSourceInitialValue<GValue>
): ILetTuple<GValue>
type ILetTuple<GValue> = [
  emit: IObserver<GValue>,
  subscribe: IObservable<GValue>,
  getValue: () => GValue,
];

Definition​

This function is our best friend to create an Observable with a stored value, that we may update anytime.

This is somehow like the let of javascript, but it works with Observables instead.

This is a shortcut for createReplayLastSource, but it returns a tuple instead of an object.

Its simply does:

function let$$<GValue>(
  ...initialValue: ICreateReplayLastSourceInitialValue<GValue>
): ILetTuple<GValue> {
  const { emit, subscribe, getValue } = createMulticastReplayLastSource<GValue>(...initialValue);
  return [
    emit,
    subscribe,
    getValue,
  ];
}

Example​

const [$firsName, firstName$] = let$$('Valentin');
const [$lastName, lastName$] = let$$(); // it's possible to omit the value, in this case, the Observable is uninitialized

const fullName$ = string$$`${firstName$} ${lastName$}`;

fullName$((value) => {
  console.log(value);
});

lastName$('Richard');
// OUT => Valentin Richard

firstName$('Bob');
// OUT => Bob Richard

Output:

Valentin Richard
Bob Richard