format-json-output

A simple CLI tool that filters and pretty-prints JSON lines from stdout while passing through any non-JSON lines as-is.

Use Case

Useful for formatting mixed stdout output from processes like npm run start:watch where JSON lines are mixed with logs or other messages.

Installation

npm install -g format-json-output

Usage

npm run start:watch | format-json-output

Behavior

• Lines containing valid JSON objects (enclosed in {}) are formatted using JSON.stringify(obj, null, 2).
• Lines without JSON or with invalid JSON are output unchanged.

Example

Input:

INFO Starting dev server...
{"event":"build","status":"success"}
WARN Watch mode enabled.

Output:

INFO Starting dev server...
{
  "event": "build",
  "status": "success"
}
WARN Watch mode enabled.