livepatch

livepatch

Patch JSON streams on the fly.

Example

var fs = require('fs');
var livepatch = require('livepatch');

fs.createReadStream('test.json')
	.pipe(livepatch(function() {
		/* Transformations goes here */

		this.rename('$.name_*', 'name'); // Renames all keys in the root starting with 'name_' to 'name'

		this.remove('$._*'); // Removes all fields in the root starting with an underscore

		// Advanced usage
		this.rewrite('$.author', function(match) {
			return {
				rename: 'author_name',
				value: match.value.toUpperCase()
			};
		});
	}))
	.pipe(fs.createWriteStream('output.json'));

Documentation

rename(path, name)

Renames all fields matched by path to name.

remove(path)

Remove all fields matched by path.

rewrite(path, rewriteFn)

Rewrite all fields matched by path using rewriteFn.

The passed function receives an argument with the following information:

key: current key name

path: current path(as an array)

value: current key value(if available)

It should return a JSON object with atleast one of the following actions:

rename: Renames the fields with the given value

remove: If true, removes the key

value: Changes the key value

path

All paths used in transformations are based on the JSONPath spec.

$ denotes the root of the object . denotes the end of a key name * denotes any range of characters

Examples

$.name Matches the name field.

$.books[*].author Matches all books authors.

$.books[*].*_name Matches all fields in a book that ends with _name.

How it works

LivePatch works by reading a JSON stream with clarinet and doing live modifications based on the current path in the stream. After patching, it immediatly serializes to the next stream the resulting JSON.

It's very useful when dealing with very large objects which came from a stream(e.g.: ElasticSearch results) that need to be modified and streamed to another place(e.g.: network). As it doesn't hold the entire data on memory you don't need to worry about loading large files.

License

Check here.