@absinthe/socket/src/notifier/observe.js

Absinthe Socket

// @flow

import type {Notifier, Observer} from "./types";

const observe = <Result, Variables: void | Object>(
  {activeObservers, ...rest}: Notifier<Result, Variables>,
  observer: Observer<Result, Variables>
) => ({
  ...rest,
  activeObservers: [...activeObservers, observer],
  isActive: true
});

export default observe;