Raynos/observ other api

l-value.ts

// `l-value` is inspired by [email protected]
// https://github.com/Raynos/observ/tree/v0.2.0

export type Listener<T> = (newValue: T) => any;
export type Unlisten = () => void;

export interface LValue<T> {
  get(): T;
  listen(listener: Listener<T>): Unlisten;
  set(newValue: T): void;
}

class LValueImpl<T> implements LValue<T> {
  private readonly _listeners: Listener<T>[];
  private _value: T;

  constructor(initialValue: T) {
    this._listeners = [];
    this._value = initialValue;
  }

  get(): T {
    return this._value;
  }

  listen(listener: Listener<T>): Unlisten {
    this._listeners.push(listener);
    return () => {
      const index = this._listeners.indexOf(listener);
      this._listeners.splice(index, 1);
    };
  }

  set(newValue: T) {
    this._value = newValue;
    this._listeners.forEach((listener) => listener(newValue));
  }
}

const lValue = <T>(initialValue: T): LValue<T> => new LValueImpl(initialValue);

export { lValue };