JavaScript / ECMAScript

JSON Log Line (Single-Line Object) in JS

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

Try it in the JS tester →

Pattern

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

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).

How the pattern 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.

Examples

Input

{"level":"info","msg":"started","port":8080}

Matches

  • {"level":"info","msg":"started","port":8080}

Input

{"event":"login","user":{"id":42}}

Matches

  • {"event":"login","user":{"id":42}}

Input

plain text log line

No match

—

Same pattern, other engines

Python (re)

Supported

See how this pattern looks (and behaves) in Python's stdlib `re` module.

Go (RE2)

Supported

See how this pattern looks (and behaves) in Go's `regexp` package (RE2 engine).

← Back to JSON Log Line (Single-Line Object) overview (all engines)