Syntek Documentation

Instanceof Expression

An instanceof expression checks if the expression is an instance of the given type. Syntek automatically casts the checked expression to the given type.

If the generics of the given type can not be inferred, they have to be provided explicitely.

Structure

InstanceofExpr = Expression 'instanceof' Type

Example

5 instanceof Object
[1, 2, 3] instanceof Array
new Dog() instanceof Animal

function foo(x: Object) {
  if x instanceof Number {
    print(x + 5)
  }
}

class Foo<T> {}

class Bar<T, E> extends Foo<T> {
  function get(): E {}
}

function foo(x: Foo<Number>) {
  if x instanceof Bar<Number, String> {
    var y = x.get() # y is inferred as String
  }
}

References

← Async Expression →