And I don't mean to execute the other language by executing a different file
type. e.g. run "cscript.exe thecode.js" from VBScript. But to actually call
a function provided from the other language.

JScript in VBScript...

Option Explicit

dim ojs

set ojs= createobject("ScriptControl")
ojs.language = "JScript"

ojs.AddCode "function x(a,b) {return 'answer = ' +(a+b);}"

msgbox(ojs.Run("x",1,2))



You might need to register the control (32 bit)

%windir%\SysWoW64\regsvr32.exe %windir%\SysWoW64\msscript.ocx

And you'll need to run it as 32 bit

%windir%\SysWoW64\cscript.exe whatever.vbs


Running VBScript in JScript? Tricky, it would depend on how you are
running the JScript, you'd probably need IE.


I've used the above method to run VBScript in other programming languages.
For instance, VFP6 calls VBScript, which then uses .Net to create a SHA256
hash.

objvb.language = "VBScript"

(The following needs to be on one line)

objvb.addcode('function fnh(x,y):
dim e,c,h:set e=createobject("System.Text.UTF8Encoding"):
set c=createobject("System.Security.Cryptography.HMACSHA256"):
c.Key=e.GetBytes_4(x):
h=c.ComputeHash_2(e.GetBytes_4(y)):
fnh=h:
end function ')

Called with...
hash = objvb.run("fnh", key, text)

Similarly VFP6 has trouble with binary streams downloaded from the
internet, but VBScript can download and save the file, without VFP6 ever
being aware.

objvb.addcode('function fnk(ohttp,f):
dim e:
set e=CreateObject("ADODB.Stream"):
e.type=1:
e.open:
e.write ohttp.ResponseBody:
e.savetofile f, 2:
set e = nothing:
end function ')

Called with...
objvb.run("fnk", httpobject, filename)


Roger