Mascara JavaScript compiler Blog

Mascara 1.2 has been released, and supports interfaces, an often requested feature.

They work as you would expect very much like interfaces in Java and C#. Basically they describe a set of methods that any class that implements the interface must provide implementations for.

Interfaces may contain function and getter/setter declarations, but not variables or nested types. (Hence ECMAScript interfaces does not allow constants as in Java). Declaration are just function signatures without a body.

Example:

interface Moveable {
  function moveTo(x: int, y:int) : void;
}
class DialogBox implements Moveable {
    function moveTo(x : int, y:int) : void {
        // implementation
    }
}

Interfaces can inherit from multiple other interfaces, and classes can implement multiple interfaces.

Syntax is defined in the documentation.