How can I use JavaScript within an Excel macro?

Question

There’s a really cool diff class hosted by Google here:

http://code.google.com/p/google-diff-match-patch/

I’ve used it before on a few web sites, but now I n

Answer 1

The Windows Scripting Engine will allow you to run the JavaScript library. It works well in my experience.

Answer 2

The simplest approach may be to embed the Javascript diff logic into a COM component directly using Javascript. This is possible via something called "Windows Script Components".

Here's a tutorial on creating WSCs.

A Windows Script Component is a COM component that is defined in script. The interface to the component is via COM, which means it is VBA friendly. The logic is implemented in any Windows Scripting Hosting -compatible language, like JavaScript or VBScript. The WSC is defined in a single XML file, which embeds the logic, the component Class ID, the methods, the registration logic, and so on.

There's also a tool available to help in creating a WSC. Basically it is a wizard-type thing that asks you questions and fills in the XML template. Myself, I just started with an example .wsc file and edited it by hand with a text editor. It's pretty self-explanatory.

A COM component defined this way in script (in a .wsc file) is callable just like any other COM component, from any environment that can dance with COM.

UPDATE: I took a few minutes and produced the WSC for GoogleDiff. Here it is.

<?xml version="1.0"?>

<package>

<component id="Cheeso.Google.DiffMatchPatch">

  <comment>
    COM Wrapper on the Diff/Match/Patch logic published by Google at http://code.google.com/p/google-diff-match-patch/.
  </comment>

<?component error="true" debug="true"?>

<registration
  description="WSC Component for Google Diff/Match/Patch"
  progid="Cheeso.Google.DiffMatchPatch"
  version="1.00"
  classid="{36e400d0-32f7-4778-a521-2a5e1dd7d11c}"
  remotable="False">

  <script language="VBScript">
  <![CDATA[

    strComponent = "Cheeso's COM wrapper for Google Diff/Match/Patch"

    Function Register
      MsgBox strComponent & " - registered."
    End Function

    Function Unregister
      MsgBox strComponent & " - unregistered."
    End Function

  ]]>
  </script>
</registration>


<public>
  <method name="Diff">
    <parameter name="text1"/>
    <parameter name="text2"/>
  </method>
  <method name="DiffFast">
    <parameter name="text1"/>
    <parameter name="text2"/>
  </method>
</public>


<script language="Javascript">
<![CDATA[


    // insert original google diff code here...


// public methods on the component
var dpm = new diff_match_patch();


function Diff(text1, text2)
{
   return dpm.diff_main(text1, text2, false);
}


function DiffFast(text1, text2)
{
   return dpm.diff_main(text1, text2, true);
}


]]>
</script>

</component>

</package>

To use that thing, you have to register it. In Explorer, right click on it, and select "Register". or, from the command line: regsvr32 file:\c:\scripts\GoogleDiff.wsc

I didn't try using it from VBA, but here is some VBScript code that uses the component.

Sub TestDiff()
    dim t1 
    t1 = "The quick brown fox jumped over the lazy dog."

    dim t2 
    t2 = "The large fat elephant jumped over the cowering flea."

    WScript.echo("")

    WScript.echo("Instantiating a Diff Component ...")
    dim d
    set d = WScript.CreateObject("Cheeso.Google.DiffMatchPatch")

    WScript.echo("Doing the Diff...")
    x = d.Diff(t1, t2)

    WScript.echo("")
    WScript.echo("Result was of type: " & TypeName(x))
    ' result is all the diffs, joined by commas.  
    ' Each diff is an integer (position), and a string.  These are separated by commas.
    WScript.echo("Result : " & x)

    WScript.echo("Transform result...")
    z= Split(x, ",")
    WScript.echo("")
    redim diffs(ubound(z)/2)
    i = 0
    j = 0
    For Each item in z
      If (j = 0) then
        diffs(i) = item
        j = j+ 1      
      Else 
          diffs(i) = diffs(i) & "," & item
        i = i + 1
        j = 0
      End If
    Next

    WScript.echo("Results:")
    For Each item in diffs
      WScript.echo("  " & item)
    Next

    WScript.echo("Done.")

End Sub

Answer 3

Here's another option to consider, though I'm not by any means stating its the best one.

• Insure that the Python version compiles in IronPython. (There shouldn't be any problems here, or only a small amount of porting at most.)
• Create an Excel add-in library using C# and reference IronPython from it.
• Wrap the necessary functionality in your C# Excel add-in.

Answer 4

My suggestion would be that whatever you do you wrap it in a COM wrapper. VBA deals best with COM objects so you could compile as a .NET Component then expose as a COM object using the interop functionality of .NET.

As an alternative you could also look into using Windows Scripting Host objects to execute a Javascript File and return you the result.