How do I copy a certain part of data from one form field to another in jquery/mootools

I have 2 form input fields one is a image upload one is a text input I need to just take the image file name from the image upload field wit开发者_开发百科hout the /images/and the .jpg

From this post: Need a basename function in Javascript

function baseName(str) {
    var base = new String(str).substring(str.lastIndexOf('/') + 1); 
    if(base.lastIndexOf(".") != -1) 
        base = base.substring(0, base.lastIndexOf("."));
    return base;
}

You can use it by inputting a string into the function like so:

var fileName = baseName("path/to/file/image.jpg");