json-mask-stream

{"ip": "198.55.125.23", "timestamp":"2014-02-24 10:29:42", "url": "http:\/\/somedomain.com"}

var fs             = require('fs');
var logstream      = fs.createReadStream('logfile.json');
var split          = new require('split')();
var JsonMaskStream = require('json-mask-stream');
var maskStream     = new JsonMaskStream('url,timestamp');
 
logstream
.pipe(split)
.pipe(maskStream)
.pipe(process.stdout) //  {"url": "http:\/\/somedomain.com", "timestamp":"2014-02-24 10:29:42"}