jipe/pp.js

Filter, extract from and pretty print a stream of JSON objects.

var util = require('util');
var Transform = require('stream').Transform;
util.inherits(JSONPrintStream, Transform);

var debug = require('debug')('jipe.pp');
var _ = require('underscore');

function JSONPrintStream(options) {
  if (!(this instanceof JSONPrintStream)) {
    return new JSONPrintStream(options);
  }

  var conf = _.extend({
    indent: 4
  }, options);

  Transform.call(this, options);
  this._writableState.objectMode = true;
  this._readableState.objectMode = false;
  this._indent = conf.indent;
}

JSONPrintStream.prototype._transform = function(obj, _, done) {
  if (obj !== JSONPrintStream.NULL) {
    debug('printing %j', obj);
    this.push(JSON.stringify(obj, null, this._indent) + '\n');
  } else {
    debug('printing null');
    this.push('null\n');
  }
  done();
};

/* null placeholder since passing in null ends the stream */
JSONPrintStream.NULL = new Object();

module.exports = JSONPrintStream;