- 2 min read

CodeWars Kata: File Path Operations

img of CodeWars Kata: File Path Operations

The problems in this Kata File-Path-Operations revolve around implementing common filename functions. Functions are needed to find the file-extension, the filename and the path to the directory.

To solve all three problems you need to find a specific pattern in a string. I choose to use Regular Expressions to solve the problems.

Regular Expressions are quite complicated to write. In order to quickly create and test regex expressions I use this website Regex 101. It allows you to quickly test your expression against multiple inputs as well as provides a documentation for the regex syntax.


export class FileMaster {

  constructor(private filepath: string) { }

  extension(): string {
   return this.filepath.match(/\.(.*)/)[1];

  filename(): string {
   return this.filepath.match(/\/([^\/]*)\./)[1];

  dirpath(): string {
   return this.filepath.match(/(.*\/)/)[1];


This code passed the test suite for the problem. However it is not suited for a production system.

The code does not work for these paths:

  • Malformed filenames (invalid filepaths, cannot be detected)
  • Files using path for Windows (Windows uses the ”- separator for paths)
  • Does not work for folders containing a ’.’ (i.e. .vscode/test.json)
  • No handling of files without file extension

There are probably even more edge cases that I missed. Therefor in an production environment you should rely on the existing functions provided by the Path Module.