consider the following code which worked with javafx 2.2.x:

Controller:

public class SomeController {

  @FXML
  public void print(String s){
    System.out.println("from javascript: "+s);
  }
}

FXML:

<?xml version="1.0" encoding="utf-8"?>

<?language javascript?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.control.Button?>

<VBox xmlns:fx="http://javafx.com/fxml"
      fx:controller="fxmltest.SomeController">
  <fx:script>
    function buttonClicked(text) {
    controller.print(text);
    }
  </fx:script>
  <children>
    <Button text="John Doe" onAction="buttonClicked('hi')"/>
  </children>
</VBox>

this was the only way to pass parameters from fxml to its controller in an onAction method and it was extremely convenient. this code is adaped from the javafx fxml tutorial at http://docs.oracle.com/javafx/2/api/javafx/fxml/doc-files/introduction_to_fxml.html#script_event_handlers
This code fails in javafx 8 (newest EAP):

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: javax.script.ScriptException: ReferenceError: "buttonClicked" is not defined in <eval> at line number 1
at javafx.fxml.FXMLLoader$ScriptEventHandler.handle(FXMLLoader.java:1536)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:203)
at javafx.scene.Node.fireEvent(Node.java:7996)
at javafx.scene.control.Button.fire(Button.java:184)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:183)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:91)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:84)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:203)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3622)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3453)
at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3405)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1697)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2473)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:312)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:237)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:354)
at com.sun.glass.ui.View.handleMouseEvent(View.java:514)
at com.sun.glass.ui.View.notifyMouse(View.java:877)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:101)
at java.lang.Thread.run(Thread.java:724)
Caused by: javax.script.ScriptException: ReferenceError: "buttonClicked" is not defined in <eval> at line number 1
at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:426)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:410)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:392)
at jdk.nashorn.api.scripting.NashornScriptEngine.eval(NashornScriptEngine.java:139)
at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
at javafx.fxml.FXMLLoader$ScriptEventHandler.handle(FXMLLoader.java:1534)
... 47 more
Caused by: <eval>:1 ReferenceError: "buttonClicked" is not defined
at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:66)
at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:328)
at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:300)
at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:287)
at jdk.nashorn.internal.runtime.ScriptObject.noSuchProperty(ScriptObject.java:1976)
at jdk.nashorn.internal.runtime.ScriptObject.noSuchMethod(ScriptObject.java:1939)
at jdk.nashorn.internal.runtime.ScriptObject.findGetMethod(ScriptObject.java:1691)
at jdk.nashorn.internal.runtime.ScriptObject.lookup(ScriptObject.java:1603)
at jdk.nashorn.internal.runtime.linker.NashornLinker.getGuardedInvocation(NashornLinker.java:75)
at jdk.internal.dynalink.support.CompositeTypeBasedGuardingDynamicLinker.getGuardedInvocation(CompositeTypeBasedGuardingDynamicLinker.java:176)
at jdk.internal.dynalink.support.CompositeGuardingDynamicLinker.getGuardedInvocation(CompositeGuardingDynamicLinker.java:124)
at jdk.internal.dynalink.support.LinkerServicesImpl.getGuardedInvocation(LinkerServicesImpl.java:138)
at jdk.internal.dynalink.DynamicLinker.relink(DynamicLinker.java:229)
at jdk.nashorn.internal.scripts.Script$\^eval\_.runScript(<eval>:1)
at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:518)
at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:202)
at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:366)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:408)
... 51 more
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: javax.script.ScriptException: ReferenceError: "buttonClicked" is not defined in <eval> at line number 1
at javafx.fxml.FXMLLoader$ScriptEventHandler.handle(FXMLLoader.java:1536)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:203)
at javafx.scene.Node.fireEvent(Node.java:7996)
at javafx.scene.control.Button.fire(Button.java:184)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:183)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:91)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:84)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:203)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3622)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3453)
at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3405)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1697)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2473)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:312)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:237)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:354)
at com.sun.glass.ui.View.handleMouseEvent(View.java:514)
at com.sun.glass.ui.View.notifyMouse(View.java:877)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:101)
at java.lang.Thread.run(Thread.java:724)
Caused by: javax.script.ScriptException: ReferenceError: "buttonClicked" is not defined in <eval> at line number 1
at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:426)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:410)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:392)
at jdk.nashorn.api.scripting.NashornScriptEngine.eval(NashornScriptEngine.java:139)
at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
at javafx.fxml.FXMLLoader$ScriptEventHandler.handle(FXMLLoader.java:1534)
... 47 more
Caused by: <eval>:1 ReferenceError: "buttonClicked" is not defined
at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:66)
at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:328)
at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:300)
at jdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:287)
at jdk.nashorn.internal.runtime.ScriptObject.noSuchProperty(ScriptObject.java:1976)
at jdk.nashorn.internal.runtime.ScriptObject.noSuchMethod(ScriptObject.java:1939)
at jdk.nashorn.internal.runtime.ScriptObject.findGetMethod(ScriptObject.java:1691)
at jdk.nashorn.internal.runtime.ScriptObject.lookup(ScriptObject.java:1603)
at jdk.nashorn.internal.runtime.linker.NashornLinker.getGuardedInvocation(NashornLinker.java:75)
at jdk.internal.dynalink.support.CompositeTypeBasedGuardingDynamicLinker.getGuardedInvocation(CompositeTypeBasedGuardingDynamicLinker.java:176)
at jdk.internal.dynalink.support.CompositeGuardingDynamicLinker.getGuardedInvocation(CompositeGuardingDynamicLinker.java:124)
at jdk.internal.dynalink.support.LinkerServicesImpl.getGuardedInvocation(LinkerServicesImpl.java:138)
at jdk.internal.dynalink.DynamicLinker.relink(DynamicLinker.java:229)
at jdk.nashorn.internal.scripts.Script$\^eval\_.runScript(<eval>:1)
at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:518)
at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:202)
at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:366)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:408)