JSON Formatter CLI

You are an assistant that generates a single-file Node.js CLI tool. Produce a script called json-formatter.js runnable with Node.js 18+ and zero external dependencies.

Requirements

Input handling

• Accept a file path as a positional CLI argument: node json-formatter.js data.json
• If no positional argument is given, read from stdin (support piping: cat data.json | node json-formatter.js)
• If no argument and stdin is a TTY (no piped data), print a usage message to stderr and exit with code 1
• If the file argument does not exist, print a human-readable error to stderr (e.g., Error: File not found — data.json) and exit with code 1. Do not print a raw stack trace.

CLI flags

Support these flags (may appear before or after the file argument):

• --help or -h — print usage information (tool name, synopsis, flag descriptions, examples) to stdout and exit with code 0
• --no-color — force disable ANSI colors even if stdout is a TTY
• --compact or -c — output minified JSON on a single line instead of pretty-printed

Parse flags manually from process.argv — do not use an argument parsing library.

JSON parsing and error reporting

• Parse the entire input string with JSON.parse()
• On parse failure, compute the line and column of the error position by counting newlines in the input up to the character offset reported in the error message
• Print the error to stderr in a clear format: Error: Invalid JSON at line 5, column 12 — Unexpected token ','
• Exit with code 1 on any error (file not found, read error, parse error)

Pretty-printing with syntax highlighting

• In default mode, output the parsed JSON with 2-space indentation
• In --compact mode, output with no whitespace (JSON.stringify(data))
• Apply ANSI color codes for syntax highlighting using these colors:
  • Property keys: bold white or bright blue (\x1b[1m or \x1b[94m)
  • String values: green (\x1b[32m)
  • Numbers: yellow (\x1b[33m)
  • Booleans (true/false) and null: cyan (\x1b[36m)
  • Brackets, braces, colons, commas: dim (\x1b[2m)
  • Reset after each token: \x1b[0m
• Implementation approach: call JSON.stringify(data, null, 2), then apply a single regex replacement pass that matches JSON tokens (quoted strings, numbers, booleans, null) and wraps them in ANSI codes. Distinguish keys from string values by checking if the match is followed by :
• Disable colors when:
  • stdout is not a TTY (!process.stdout.isTTY)
  • --no-color flag is passed
  • NO_COLOR environment variable is set (respect the NO_COLOR convention)

Code style

• Use CommonJS (require) so the script runs without "type": "module" in package.json
• Keep it under 150 lines
• Add a comment header: tool name, one-line description, usage example