But an object *is* a key/value structure.

It's a case of:

const lookup = {

'foo': 1,

'bar': 2,

'baz': 3

};

versus

const lookup = new Map();

lookup.set('foo', 1);

lookup.set('bar', 2);

lookup.set('baz', 3);

To my mind, at least, the object declaration is a lot more readable than the Map.