JS Bin// source http://jsbin.com/kulujin

JavaScript Subscribe and unsubscribe using function assignment and call.js

// this pattern subscribes adds item to an array when subscribe function
// is is assigned to a variable, and unsubscribes when this variable is eventually called

// taken from Redux tutorial
// https://egghead.io/lessons/react-redux-implementing-store-from-scratch

// also discussed here
// https://stackoverflow.com/questions/35304790/es6-redux-returning-a-function-to-remove-event-listener

let listeners = []

function subscribe(listener) {
  listeners.push(listener);
  return () => {
    listeners = listeners.filter(l => l !== listener);
  };
};

const remove = subscribe('myListener');
console.log(listeners) // myListener in the array
remove()
console.log(listeners) // myListener no longer in the array

// pretty cool