JSON format command line utility

format-json.coffee

fs = require "fs"

inFile = process.argv[2] # Read the input file name from the 1st command line parameter.
outFile =  process.argv[3] # Read the output file name from the 2nd optional command line parameter.

fs.readFile inFile, "utf8", (err, data) -> # Read the input file content.
  if err
    console.log err # Log error to console.
  else
    try
      object = JSON.parse data # Parse the input file content as JSON.
      result = JSON.stringify object, null, "  " # Serialize the object to JSON again using double space indentation.
    catch e
      result = "Invalid JSON" # Show the error message if JSON parsing fails.
    if outFile
      fs.writeFile outFile, result # If ouput file name is defined, write the result to it.
    else
      console.log result # Otherwise write the result to console.