Logs

JSON Log Line (Single-Line Object)

Match a single-line JSON object — typical of structured logging from services like slog, Bunyan, or Pino.

Available in

JavaScript / ECMAScript code

jsJavaScript

const re = new RegExp("^\\{(?:[^{}]|\\{[^{}]*\\})*\\}$", "");
const input = "{\"level\":\"info\",\"msg\":\"started\",\"port\":8080}";
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"^\{(?:[^{}]|\{[^{}]*\})*\}$")
input_text = "{\"level\":\"info\",\"msg\":\"started\",\"port\":8080}"
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(`^\{(?:[^{}]|\{[^{}]*\})*\}$`)
	input := `{"level":"info","msg":"started","port":8080}`
	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

^\{(?:[^{}]|\{[^{}]*\})*\}$

Raw source: ^\{(?:[^{}]|\{[^{}]*\})*\}$

How it works

^\{ anchors to an opening brace at start. (?:[^{}]|\{[^{}]*\})* matches any non-brace chars or one level of nested braces (so `{"a":{"b":1}}` matches but deeper nesting may not). \}$ anchors to the closing brace at end. Quick filter for log-line shape; pair with JSON.parse to validate fully.