The HTTP route is probably the right way to go. You can easily set up a small Server using Node.js Node.js, and have it spawn your AHK script using one of the Child Process functions. I don't know how the Chrome Extension security model works, so you might have to mitigate cross-site scripting concerns. I think that's solvable, but haven't done so.

Yes, ahk supports running external executables and capturing their output. See the documentation

So, you use that to run your node command (something like c:\path_to_node\node.exe c:\path_to_script\script.js)

Your output is only the Process ID (PID). You need to run your .js in a WSH wrapper, and your .js needs to return StdOut as follows:

Here is the AHK "secret sauce" RunWaitStdOut:

MsgBox % RunWaitStdOut("C:\path_to_script\index.js")

RunWaitStdOut(command)
{
    shell := ComObjCreate("WScript.Shell")
    exec := shell.Exec(ComSpec " /c node " command)
    return exec.StdOut.ReadAll() 
}

And in the meantime, the end of your .js should have something like the following generating the StdOut:

    process.stdout.write("The Result this javascript returns to AHK is " + myValue);

And remember, StdOut is a string, so if your myValue is a number or such, you may need the toString() method (as OP noticed, per OP's comment):

    process.stdout.write( myValue.toString() );

Hth,