Why does accessing with the member access operator throw error

In the following example we are accessing properties of an object but why does accessing the object with the Member Access throw an error:

 var d = {a: 10, b: 20, c:30};
         
         var keys = Object.getOwnPropertyNames(d);
         
         for(let i = 0; i < keys.length; i++){
            console.log(d[keys[i]]);
            //console.log(d.keys[i]); //throws error
         }

For example shown above, i would assume this would be because if we accessed it with the member access operator it would try access d immediately without initializing keys[i]. Would this be correct?