Finding only Alphabets in File name

Hi,

I am trying to find if any alphabets comes in the file name i should get an alert. As well as only numbers also i need to make a script.

I tried writing the code like this:

It storing the file name. But not getting alert !!!!

Does any one help on this.

#target photoshop

var myInputFolder = Folder.selectDialog ("Select Web Folder");

if(myInputFolder!=null){

    var myFiles = myInputFolder.getFiles(/\.(tif)$/i);

    for(var fileIndex=0;fileIndex<myFiles.length;fileIndex++)

    {

        var currentFile = myFiles[fileIndex];

        if(currentFile instanceof File)

        {

                if(currentFile.hidden) continue;

var doc = app.open(currentFile);   

    myDoc = doc.name;

    var fileNameNoExt = myDoc.split('-')[0]; 

    var dashIndex = fileNameNoExt.split('-'); 

    var imageNum = Number(fileNameNoExt.split('-')[dashIndex.length-1])  

    alert(imageNum)

    }

}

}

I am getting before "-" file name in alert. But not throwing error if file name contains Alphabets.

Thanks in Advance,

Suresh.