callingChangeTriggerFunction.js

// Calling increment() will dispatch the following action:
// {type: 'INCREMENT', payload: {value: 10}}
increment({value: 10});

/*
  This will be picked up by your reducer:
  
  reducer: (state, payload, action) => {  
    return state + payload.value;
  }
  
  And will trigger the store.subscribe() function to output the new state:
  10
*/