NaN values cause jsonpatch.observe confusion

[mbeerta-factset]

When dealing with NaN values, generated patches always have a replace operation on nodes containing those.

Reproduction:

const jsonpatch = require('fast-json-patch');

class DocumentImpl {

  constructor () {
    this.data = [
      {
        "key" : "value",
        "member" : NaN
      }
    ]
  }
}

const document = new DocumentImpl();
var observer = jsonpatch.observe(document);

document.data.push({
      "key" : "value2",
      "member" : 12345
    });

const patch = jsonpatch.generate(observer);
console.log(patch);

which generates the following javascript object

[ { op: 'replace', path: '/data/0/member', value: NaN },
  { op: 'add',
    path: '/data/1',
    value: { key: 'value2', member: 12345 } } ]

the first op should not be there. Converting the object to a json string leads value to be null , which is probably also the root cause.

[alshakero]

Hi! Your diagnosis is on point. JSON-Patch acts like native JSON.parse/stringify where NaN is not supported. That's why NaN causes trouble for it. See

https://github.com/Starcounter-Jack/JSON-Patch#undefineds-js-to-json-projection

I don't think we plan to support Javascript objects. This is only to observse JSON documents. For the same reason we don't support functions and Date objects observation.