jsinterop.annotations

Annotation Type JsFunction

@Retention(value=RUNTIME)
 @Target(value=TYPE)
 @Documented
public @interface JsFunction

JsFunction marks a functional interface as being the definition of a JavaScript function.

There are some limitations exists on JsFunction to make them practical and efficient:

• A JsFunction interface cannot extend any other interfaces.
• A class may not implement more than one JsFunction interface.
• A class that implements a JsFunction type cannot be a JsType (directly or indirectly).
• Fields and defender methods of the interfaces should be marked with JsOverlay and cannot be overridden by the implementations.

As a best practice, we also recommend marking JsFunction interfaces with FunctionalInterface to get improved checking in IDEs.

Instanceof and Castability:

Instanceof and casting for JsFunction is effectively a JavaScript 'typeof' check to determine if the instance is a function.