Property 'onNextChange' is missing in type

[lifeeric]

I'm getting the below error don't know why and what's happening, how get over it? I'm using TS

/test/ac3-state-management-examples/apollo-local-state/src/tests/createMockReactiveVar.ts
TypeScript error in /test/ac3-state-management-examples/apollo-local-state/src/tests/createMockReactiveVar.ts(11,3):
Property 'onNextChange' is missing in type '(newValue?: T | undefined) => T' but required in type 'ReactiveVar<T>'.  TS2741

     9 |   let currentValue: T | undefined = defaultValue;
    10 | 
  > 11 |   return function mockReactiveVar (
       |   ^
    12 |     newValue?: T
    13 |   ) : T {
    14 |     if (newValue) {

[hacking-robot]

Same here. I didn't change anything, i just started the client https://github.com/apollographql/ac3-state-management-examples/tree/master/apollo-remote-state
And why are the examples written in typescript ?

[billhong6981]

undefined is not type ReactiveVar, so please change to any
export function createMockReactiveVar (defaultValue?: T): any {

[stemmlerjs]

Fixed #35