Text Processingflags: gm

Keep-a-Changelog Entry Header

Match Keep-a-Changelog style version headers like `## [1.2.3] - 2024-01-15` or `## 2.0.0`.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("^##\\s+\\[?([\\w.\\-]+)\\]?(?:\\s*-\\s*(\\d{4}-\\d{2}-\\d{2}))?", "gm");
const input = "## [1.2.3] - 2024-01-15\\n## [Unreleased]";
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"^##\s+\[?([\w.\-]+)\]?(?:\s*-\s*(\d{4}-\d{2}-\d{2}))?", re.MULTILINE)
input_text = "## [1.2.3] - 2024-01-15\n## [Unreleased]"
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(`(?m)^##\s+\[?([\w.\-]+)\]?(?:\s*-\s*(\d{4}-\d{2}-\d{2}))?`)
	input := `## [1.2.3] - 2024-01-15\n## [Unreleased]`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}

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

Pattern

regexengine-agnostic

^##\s+\[?([\w.\-]+)\]?(?:\s*-\s*(\d{4}-\d{2}-\d{2}))?   (flags: gm)

Raw source: ^##\s+\[?([\w.\-]+)\]?(?:\s*-\s*(\d{4}-\d{2}-\d{2}))?

How it works

^## matches the markdown H2 marker. \s+ requires whitespace. \[? optionally matches an opening bracket. ([\w.\-]+) captures the version (semver, calendar version, or label like `Unreleased`). \]? optionally matches the closing bracket. (?:\s*-\s*(\d{4}-\d{2}-\d{2}))? optionally captures an ISO date.