Pass Nothing from Javascript to VBScript in IE9

I have a framework written in VBScript. Inside some function in this framework, a parameter of the function is checked for Nothing in an If statement and then some actions are executed.

Code that uses the framework is written in JavaScript. So I need to pass Nothing to the function to perform some actions. In Internet Explorer 8 and earlier versions, the following approach worked:

<script type="text/vbscript">
Function Test(val)
If (IsNull(val)) Then
Test = "Null"
ElseIf (IsObject(val)) Then
If (val Is Nothing) Then
Test = "Nothing"
End If
End If
End Function


Dim jsNothing
Set jsNothing = Nothing
msgBox(Test(jsNothing))
msgBox(Test(Null))
</script>




<script type="text/javascript">
alert(Test(jsNothing));
</script>

In Internet Explorer before version 9, the output will: Nothing, Null, Nothing.

In Internet Explorer 9: Nothing, Null, Null.

How can I pass Nothing from JavaScript to VBScript in Internet Explorer 9?

There is an example of a framework function. I can not change it, because it is widely used in application.

Function ExampleFunction(val)
If (val Is Nothing) Then
ExampleFunction = 1
Else
ExampleFunction = 0
End If
End Function
11517 次浏览
小开

Use a value such as zero or even a negative number. That would allow for you to simply use falsy evaluations, and then you don't have to worry about different browsers and their quirks in evaluating the NULL object.

小开

Unfortunately, you are probably stuck here - JavaScript does not have a "Nothing" equivalent. See this article for more information.

However, the following may work. In your VBScript code, create a function called "GetNothing" that returns "Nothing". In your JavaScript code, use "var jsNothing = GetNothing()". It comes from this article.

小开

I don't have access to Internet Explorer right now, so I can't test this, but try to write a function like this:

<script type="text/vbscript">
Function CallWithNulls(fn, arg1, arg2, arg3)
If (isNull(arg1)) arg1 = Nothing
If (isNull(arg2)) arg2 = Nothing
If (isNull(arg3)) arg3 = Nothing
fn(arg1, arg2, arg3)
End Function
Function IsNothing(arg1, arg2, arg3)
return arg1 is Nothing
End Function
</script>


<script type="text/javascript">
alert(CallWithNulls(IsNothing, null, 1, 2));
</script>

Of course, I don't know if VBScript allows calling functions like that... and you'd have to deal with more/fewer arguments.

小开

As an example, something like this will work, but if the browser is Internet Explorer 11 or later you will need the 'meta' tag.

<html>


<head>
<meta http-equiv="x-ua-compatible" content="IE=10">
<title>Pass JavaScript to VBScript</title>


<script>
var val = "null";


window.alert("Test: " +  val);
</script>


<script type="text/vbscript">


PassNothing(val)


Sub PassNothing(value)
If LCase(value) = "null" Then
MsgBox "Java passed 'null' so VBScript = 'Nothing'"
Else
Msgbox "Nothing received"
End If
End Sub


</script>


</head>


</html>

提交答案