Observe an object tree for changes and generate JSON Patches (RFC 6902). Uses Harmony Proxy, available in NodeJS version 6.4 and above.

Usage

const {observe} = require("jsonpatch-observe");

let observable = observe({});
observable.$subscribe(patch => console.log(patch));
observable.a = {b:1};		//prints {op:"add", path:"a", value:{b:1}}
observable.a.b = 2;		//prints {op:"add", path:"a/b", value:2}
delete observable.a;		//prints {op:"remove", path:"a"}

Note that the properties of an Observable are also Observables. This is how it's able to detect when you do observable.a.b = 2.

Unobserved Properties

You can exclude certain properties from observe as follows:

require("jsonpatch-observe").config.excludeProperty = function(obj, prop) {
	//return true to exclude the property
}

Splice Patch

The JSONPatch standard does not specify a "splice" operation. Without splice, Array changes are represented as a series of individual "add", "replace", and "remove" operations, which can be quite inefficient to apply.

This module supports generating the splice patch. Enable it as follows:

require("jsonpatch-observe").config.enableSplice = true;

The splice patch has the following format:

{
	op: "splice",
	path: "/myarr/3",		//path to array index
	remove: 2,			//number of elements removed
	add: ['a','b','c']		//elements added
}

I created a fork of Starcounter-Jack JSONPatch library capable of consuming this non-standard splice patch.