Typescript double return type object check

interface TypeOne {
  name: string;
  typeOneProp: any;
}

interface TypeTwo {
  name: string;
  typeTwoProp: any;
}

async function foo(): Promise<TypeOne | TypeTwo> {
   return this.service.get();
}

async function bar(): Promise<any> {
   const data = await foo();
   
   if(data?.typeOneProp) { // errors shown below
      return data.typeOneProp;
   }
}

Property 'typeOneProp' does not exist on type 'TypeOne | TypeTwo'.

Property 'typeOneProp' does not exist on type 'TypeTwo'. ts(2339)

how can i show typescript which return type foo() had?

already tried Object.keys to see if typeOneProp exists but data remains as TypeOne | TypeTwo

data intelisense only shows name as a property sugestion as is a common property between both types

// package.json
"typescript": "^4.4.4"

>Solution :

Use the in operator to check if the property exists on the object (TS playground):

if('typeOneProp' in data) {
  return data.typeOneProp;
}