jsonmap

streaming command line newline-delimited json transformer utility

you must pipe newline-delimited JSON data in (one JSON stringified object per line). you will receive the same format out

installation

$ npm install jsonmap -g

usage

this will be each line of JSON that gets parsed out of the incoming newline-delimited json stream. you can also use _ as a shorthand for this, and you are allowed to require things.

there are two 'modes', the first is where you modify this:

$ echo '{"foo": "bar"}\n{"baz": "taco"}' | jsonmap "this.pizza = 1"
{"foo":"bar","pizza":1}
{"baz":"taco","pizza":1}

the second mode is where you return a new object:

$ echo '{"foo": "bar", "cat": "yes"}\n{"baz": "taco", "cat": "yes"}' | jsonmap "{cat: this.cat}"
{"cat":"yes"}
{"cat":"yes"}

if your code gets too complex and you'd rather use an external file you can also just specify a module to get required:

$ echo '{"foo": "bar"}\n{"baz": "taco"}' | jsonmap --file=transform.js
{"foo":"bar","pizza":1}
{"baz":"taco","pizza":1}

the above will work if transform.js has the following contents:

module.exports = function() {
  this.pizza = 1
}

if you have es6 template strings enabled on your platform (e.g. iojs), template strings will work as well

$ echo '{"meal": "pizza"}\n{"meal": "taco"}' | jsonmap '`i love ${this.meal}`'
"i love pizza"
"i love taco"

if you want to provide a through2 function in a file for more control, or async, you can

$ echo '{"foo": "bar"}\n{"baz": "taco"}' | jsonmap --file=transform.js --through
{"foo":"bar","pizza":1}
{"baz":"taco","pizza":1}

the above will work if transform.js has the following contents:

module.exports = function(obj, enc, next) {
  var self = this;
  if(obj.foo === 'bar') return next() // skip the bar
  process.nextTick(function(){
    self.push({ count: obj.pizza })
    next()
  })
}

you disable JSON parsing (to e.g. process a file line by line as JS strings) by passing jsonmap --no-parse