The final example is the correct way to do it. Whew, a relief, have some claps!

Why do you use pictures of code, though? Not so useful if you want to cut and paste it.

Just a note that you look up in the table twice, however. It's a tiny bit wasteful.

A little faster is this:

if (c = countryCodes[country])
    return c;
throw new Error('Invalid country')

with just one table lookup.