ActionScript 3: Turning a String into and Operator? - string

Question

I'm trying to create a simple calculator program in ActionScript for a school project, and I'm struggling to find a concise way to take an equation from an array such as this: "4","+","2"; and manipulate it so that the answer to the equation can be deduced. The problem is taking the String "+" from the equation array and turning it into a usable operator. At the moment, when an operator button is pressed on the calculator GUI it adds the operator to the equation array as a String (i.e. pressing the '÷' button will add "/" to the equation array).
I looked for an answer to this on Google and found something about a JavaScript function that I used in the code below (in lines 1 and 4), but all I end up with in the Output feed is "null", or "0" depending on whether I changed the variable 'answer' to a String, or a Number.
Here's the code I have so far:
import flash.external.ExternalInterface;
var equationArray:Array = new Array("4","+","2");
var answer:Number = ExternalInterface.call("eval",equationArray[0] + equationArray[1] + equationArray[2]);
trace(answer);
I'd prefer to use something like this rather than writing a long if statement to pick between different operators if that's possible. Thanks for the help!

Answer 1

I did some research and realized that your code doesn't work only in Chrome.
There is an error
SecurityError: Error #2060
at flash.external::ExternalInterface$/call()
at FlexTemp/preinitializeHandler()
at FlexTemp/___FlexTemp_Application1_preinitialize()
at flash.events::EventDispatcher/dispatchEvent()
at mx.core::UIComponent/dispatchEvent()
at mx.core::UIComponent/initialize()
at spark.components::Application/initialize()
at FlexTemp/initialize()
at mx.managers.systemClasses::ChildManager/childAdded()
at mx.managers.systemClasses::ChildManager/initializeTopLevelWindow()
at mx.managers::SystemManager/initializeTopLevelWindow()
at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::kickOff()
at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::preloader_completeHandler()
at flash.events::EventDispatcher/dispatchEvent()
at mx.preloaders::Preloader/timerHandler()
at flash.utils::Timer/tick()
but if I switch of PepperFlash\14.0.0.145\pepflashplayer.dll in chrome://plugins/
all works fine.
I think there are some problems with pepflashplayer.dll

Answer 2

In your flash file:
import flash.external.ExternalInterface;
import flash.text.TextField;
var equationArray:Array = new Array("4","-","8");
var answer:Number = ExternalInterface.call("myJsFunction",equationArray[0] , equationArray[1] , equationArray[2])
var tf:TextField = new TextField();
addChild(tf as TextField);
tf.text = answer.toString();
In the HTML page (into the ):
<script type="text/javascript">
function myJsFunction(arg1,arg2,arg3){
return eval(arg1+arg2+arg3);
}
</script>
Is this what you try to do?
Using eval like in your code I didn't get the correct answer.
When you run as here above on localhost/server this will give you the answer.