proxyequal
=====

Shallow equal is a good thing, but it compares thing you don't need.

Proxy equal - "MobX"-like solution, which will "magically" compare only used keys.


Usage

* Wrap an object with proxyState
* Run some computations using providing proxyObject.
proxyState returns object with shape
* state - a double of provided state, with _tracking_ enabled
* affected - list of used keys in a state.
* seal - disables tracking
* unseal - enabled tracking
* replaceState(newState) - replaces top level state, maintaining rest of data.
* reset - resets tracked keys

* proxy will collect all referenced or used keys
* proxyEqual will compare all used "endpoint" keys of 2 objects
* proxyShallow will compare all used __NON__ "endpoint" keys of 2 objects.

The difference between proxyEqual and proxyShallow is in _expectations_.
* proxyShallow is similar to shallowEqual, it compares the top level objects. Might be they are still the same.
* proxyEqual working on variable-value level, performing (very) deep comparison of objects.

Extra API

- spreadGuardsEnabled(boolean=[true]) - controls spread guards, or all-keys-enumeration, which makes proxyEqual ineffective.
- sourceMutationsEnabled(boolean=[false]) - controls set behavior. By default proxied state is frozen.

When to use proxyequal

When you have a big state, for example redux state, but some function (redux selector, or mapStateToProps)
uses just a small subset.

Here proxyequal can shine, detecting the only used branches, and comparing only the used keys.

Example

``js
import {proxyState, proxyEqual, proxyShallow} from 'proxyequal';

// wrap the original state
const trapped = proxyState(state);

// use provided one in computations
mapStateToProps(trapped.state);

// first shallow compare
proxyShallow(state, newState, trapped.affected);

// next - deep compare
proxyEqual(state, newState, trapped.affected);
`


$3


`js
const trapped = proxyState(state);
// do something
workWith(trapped.state);

trapped.seal();

// now tracking is disabled

trapped.unseal();
// and enabled
`

Speed

Uses ES6 Proxy underneath to detect used branches(as MobX), and search-trie to filter out keys for shallow or equal compare.

So - it is lighting fast.

Limitations

Unfortunately, due to Proxy wrappers all objects will be unique each run.
`js
shallowEqual(proxyState(A), proxyState(A)) === false
`
There is a undocumented way to solve it, used internally in memoize-state library.
Once it will be proven to work stable - we will expose it.

Compatibility

Requires Proxy` support, so the proxy-polyfill is included in the common bundle for Internet Explorer 11. How this works may change in future, see issue #15 "ProxyPolyfill is unconditionally imported" for details.

Licence

MIT