object diff

Get the minimal patch to extend literal object A with to transform it into
literal object B

Consider an object retrieved from a server:

``js
{
name: 'Peter',
age: 26,
height: 187,
}
`

Now the user changes stuff using some frontend (e.g. a HTML form) and ends with:

`js
{
name: 'Peter',
age: 27,
height: 186,
}
`

When they hit save, you only want to send off the changed parts to the servers,
to save bits (because you're indeed a programmer), but also to avoid any
unnecessary "merge conflicts" at the server.

Imagine two users changing the same object; if they did not change the exact
same keys of the object, the last user won't erase the first user's changes - in
a lot of cases, that's the expected behavior.

Usage

`js
import diff from 'object-diff'

const a = {
speed: 4,
power: 54,
height: undefined,
level: 1,
}

const b = {
speed: 4, // unchanged
power: 22, // changed
level: undefined, // changed
weight: 10, // added
}

diff(a, b)
/*
{
power: 22,
level: undefined,
weight: 10,
}
*/

// using a custom equality function

const past = '2016-04-24T10:39:23.419Z'

import custom from 'object-diff'
custom(
(a, b) => {
if (a instanceof Date && b instanceof Date) {
return a.getTime() === b.getTime()
}
return a === b
},
{
then: new Date(past),
},
{
then: new Date(past),
},
)
/*
{}
*/
`

Compatibility

Versions 0.0.4 and 1.0.0` are functionally equivalent, without known issues,
but are CommonJS modules and compatible with older runtimes.