I'm trying to create a function to add a new property with no value yet, into an empty object, but it keeps returning undefined

below is the code i've written

const obj1={};

function addData (object,prop1,value){
    object[prop1]=value;
};

console.log(addData(obj1,"Person 1",""))

i've tried writting this code outside the function and it works

obj1["Person 1"]="";
obj1["Person 2"]="";

it will return as below

{'Person 1' : '' , 'Person 2' : ''}

Why does the function return undefined whereas writing it manually works?