Interface Function

rhino/src/main/java/org/mozilla/javascript/Function.java:18–64

This is interface that all functions in JavaScript must implement. The interface provides for calling functions and constructors. @see org.mozilla.javascript.Scriptable @author Norris Boyd

 * @author Norris Boyd
 */
public interface Function extends Scriptable, Callable, Constructable {
    /**
     * Call the function.
     *
     * <p>Note that the array of arguments is not guaranteed to have length greater than 0.
     *
     * @param cx the current Context for this thread
     * @param scope the scope to execute the function relative to. This is set to the value returned
     *     by getParentScope() except when the function is called from a closure.
     * @param thisObj the JavaScript {@code this} object
     * @param args the array of arguments
     * @return the result of the call
     */
    @Override
    Object call(Context cx, VarScope scope, Scriptable thisObj, Object[] args);

    /**
     * Call the function as a constructor.
     *
     * <p>This method is invoked by the runtime in order to satisfy a use of the JavaScript {@code
     * new} operator. This method is expected to create a new object and return it.
     *
     * @param cx the current Context for this thread
     * @param scope an enclosing scope of the caller except when the function is called from a
     *     closure.
     * @param args the array of arguments
     * @return the allocated object
     */
    @Override
    Scriptable construct(Context cx, VarScope scope, Object[] args);

    /**
     * Return the scope in which this function was declared or closed over. This is the
     * "[[Environment]]" defined in https://tc39.es/ecma262/#sec-ecmascript-function-objects.
     * Although this is currently precisely equal to the parent scope (or "__parent__") of an object
     * it is useful to distinguish the two concepts as parent scopes are no longer supported by the
     * spec in general and present a significant barrier to future optimisations.
     */
    default VarScope getDeclarationScope() {
        return this.getParentScope();
    }

    /** Return whether this function can be called as a constructor. */
    default boolean isConstructor() {
        return true;
    }
}