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

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);

Don't forget to disable

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.

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.MIT