Function on

src/effector/createUnit.ts:227–247

(
  store: Store<State>,
  methodName: string,
  nodeSet: CommonUnit | CommonUnit[],
  fn: Function,
  errorTitle: string,
)

  return finalEvent
}
function on<State>(
  store: Store<State>,
  methodName: string,
  nodeSet: CommonUnit | CommonUnit[],
  fn: Function,
  errorTitle: string,
) {
  assertNodeSet(nodeSet, `${errorTitle} ${methodName}`, 'first argument')
  assert(isFunction(fn), 'second argument should be a function', errorTitle)
  deprecate(
    !getMeta(store, 'derived'),
    `${methodName} in derived store`,
    `${methodName} in store created via createStore`,
    errorTitle,
  )
  forEach(Array.isArray(nodeSet) ? nodeSet : [nodeSet], trigger => {
    store.off(trigger)
    updateStore(trigger, store, 'on', callARegStack, fn)
  })
  return store
}

export const requireExplicitSkipVoidMessage =
  'undefined is used to skip updates. To allow undefined as a value provide explicit { skipVoid: false } option'