I'd like to remove the filename from a path using JavaScript

Question

Using Javascript I'd like to remove the filename from the end of a string (path+filename), leaving me just the directory path.

Would regular expressions be ideal? Or, is there a simpler means of doing this using the string object?

Thanks for any help!

----ANSWERED & EXPLAINED---

The purpose of this code was to open finder to a directory. The data I was able to extract included a filename - since I was only trying to open finder (mac) to the location, I needed to strip the filename. Here's what I ended up with:

var theLayer = app.project.activeItem.selectedLayers[0];
//get the full path to the selected file
var theSpot = theLayer.source.file.fsName;
//strip filename from the path
var r = /[^\/]*$/;
var dirOnly = theSpot.replace(r, '');
//use 'system' to open via shell in finder
popen = "open"
var runit = system.callSystem(popen+" "+"\""+dirOnly+"\"");

Answer 1

I know this is a very old question and has already been answered, however my requirement was to remove the file if it exists in the given path or don't do anything if its folder already.

The accepted answer's regex didn't work for me so I used this one:

let FilePathString = '/this/is/a/folder/aFile.txt';
let FolderPathString = '/this/is/a/folder/';
const RegexPattern = /[^\/](\w+\.\w+$)/i;
console.log(FilePathString.replace(RegexPattern, '')); // '/this/is/a/folder/'
console.log(FolderPathString.replace(RegexPattern, '')); // '/this/is/a/folder/'

Answer 2

var urlstr = '/this/is/a/folder/aFile.txt';
var r = /[^\/]*$/;
urlstr.replace(r, ''); // '/this/is/a/folder/'