changeset

Generate diff changesets for javascript objects, decomposing diffs into a series of puts and delete operations. The format is similar to the levelup batch operation list for bulk operations.

Handles circular references of Objects and Arrays.


Example

Take a diff of two objects and produce a list of transformation operations:

`` js
var diff = require('changeset');
var a = {
name: 'Eugene',
number: 42,
tags: ['tag1', 'tag2', 'tag3'],
scores: {
tetris: 1000,
carmageddon: 3
}
};

var b = {
name: 'Susan',
number: 43,
tags: ['tag1', 'tag4'],
scores: {
carmageddon: 3,
zelda: 3000
},
age: 37
};

var changes = diff(a, b);
expect(changes).to.deep.equal([
{ type: 'put', key: ['name'], value: 'Susan' },
{ type: 'put', key: ['number'], value: 43 },
{ type: 'put', key: ['tags', '1'], value: 'tag4' },
{ type: 'del', key: ['tags', '2'] },
{ type: 'del', key: ['scores', 'tetris'] },
{ type: 'put', key: ['scores', 'zelda'], value: 3000 },
{ type: 'put', key: ['age'], value: 37 }
]);
`

Apply an operational changeset and apply it to an object to get a transformed object:

` js
var diff = require('changeset');

var changes = [
{ type: 'put', key: ['name'], value: 'Susan' },
{ type: 'put', key: ['number'], value: 43 },
{ type: 'put', key: ['tags', '1'], value: 'tag4' },
{ type: 'del', key: ['tags', '2'] },
{ type: 'del', key: ['scores', 'tetris'] },
{ type: 'put', key: ['scores', 'zelda'], value: 3000 },
{ type: 'put', key: ['age'], value: 37 }
];

var a = {
name: 'Eugene',
number: 42,
tags: ['tag1', 'tag2', 'tag3'],
scores: {
tetris: 1000,
carmageddon: 3
}
};

// apply the changes to a
var b_ = diff.apply(changes, a);

var b = {
name: 'Susan',
number: 43,
tags: ['tag1', 'tag4'],
scores: {
carmageddon: 3,
zelda: 3000
},
age: 37
};

// the transformed object should now equal b
expect(b_).to.deep.equals(b);
`

By default `apply` will return a new modified object after applying the
changeset. If you want to modify the destination, pass true as the third
parameter:

` js
// apply the changes to a and modify a
var b_ = diff.apply(changes, a, true);
// a is now modified, and b_ is the same as a
expect(b_).to.equal(a);
``