### Operator: `in`
`x in y` returns `true` if `x` is a valid property of `y` or its prototype chain.
```JavaScript
> "foo" in {foo: 3}
true
> 2 in ["a", "b", "c"]
true
```

### Operator: `typeof`
`typeof x` or `typeof(x)` returns the type as a string.

### Operator: `instanceof`
`x instanceof y` returns true if `x` is an object of type `y`.
```JavaScript
> class A {}
> (new A) instanceof A
true
```

### Operator: `void`
`void x` or `void(x)` evaluates expression `x` and returns `undefined`.

### Keyword: `this`
Refers to the current object.

# Keyword: `super`
Refers to the parent of the current object.
Usually to call the parent constructor:
```JavaScript
> super(props)
```
but also can be used to call functions on the parent:
```JavaScript
> super.foo()
```