Getter functions unsupported as members of an object

There doesn't seem to be a way to generate a getter function as a member of an object.

For example -

```ruby
obj = { getter:  -> () { return true } }
```

This generates

```js
obj = { getter() { return true }};
```

It doesn't seem possible to generate

```js
obj = { get getter() { return true }};
```

The intent is to be able to write

```js
let a = obj.getter;
```