Generate JSON-patch from two objects

Question

Given two Javascript objects ( A and B ), is there a way to generate the JSON patch , so that when that patch is applied to A it would change the object's properties to that of object B ?

For example, given hypothetical JSONPatch function (perhaps being a function of similar name to one of those linked below), what is desired is the generate_patch function.

patch = generate_patch(A, B) JSONPatch.apply(patch, A) # modifies A so that it has the same properties as B.

In this question A and B are Javascript objects. A patch created by RFC6902 is JSON that would indicate an array of operations which when applied to A that object would become B . The generate_patch function need not return JSON though, rather for efficiency could return a Javascript object that becomes the RFC6902 JSON-patch document when JSON.stringify is called on it.

The projects I have found on the topic are:

• https://github.com/bruth/jsonpatch-js - only patches (does not generate a patch)
• http://jsonpatchjs.com/ - same
• https://github.com/Starcounter-Jack/Fast-JSON-Patch - observes an object, does not take two different objects

Answer 1

Turning my comment into an answer...

This code https://www.npmjs.org/package/rfc6902 seems to be a full javascript implementation of both patch and diff for the stated RFC.

I haven't used it myself, but the documentation makes it look like what you asked for.

Answer 2

Since version 0.3.9, https://github.com/Starcounter-Jack/Fast-JSON-Patch has a compare method which returns a difference between 2 objects. If I understand correctly, that may be what you were looking for

Answer 3

I have also written a library to generate patches: https://github.com/gregsexton/json-patch-gen

I found out about 'rfc6902' after having written and used json-patch-gen. I'm not sure how they compare: it may be worth trying out both to see if one fits your needs better.