File & Path

File Extension

Captures the file extension from a filename.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("\\.([A-Za-z0-9]+)$", "");
const input = "document.pdf";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

Python (re) code

pyPython

import re

pattern = re.compile(r"\.([A-Za-z0-9]+)$")
input_text = "document.pdf"
for m in pattern.finditer(input_text):
    print(m.group(0))

Stdlib `re` module — no third-party dependency. Works on Python 3.6+.

Go (RE2) code

goGo

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`\.([A-Za-z0-9]+)$`)
	input := `document.pdf`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

Uses `regexp.MustCompile` (panics on bad patterns at startup) and `FindAllString` for all matches.