Package Exports

@indutny/sneequals
@indutny/sneequals/dist/src/index.js

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Readme

@indutny/sneequals

Sneaky equals comparison between objects that checks only the properties that were touched.

Inspired by proxy-compare.

Installation

npm install @indutny/sneequals

Usage

One object comparison

import { watch } from '@indutny/sneequals';

const originalData = {
  nested: {
    prop: 1,
  },
  avatar: {
    src: 'image.png',
  },
};

const { proxy, watcher } = watch(originalData);

function doSomethingWithData(data) {
  return {
    prop: data.nested.prop,
    x: data.avatar,
  };
}

const result = watcher.unwrap(doSomethingWithData(proxy));

// Prevent further access to proxy
watcher.stop();

const sneakyEqualData = {
  nested: {
    prop: 1,
    other: 'ignored',
  },
  avatar: original.avatar,
};

console.log(watcher.isChanged(originalData, sneakyEqualData)); // false

const sneakyDifferentData = {
  nested: {
    prop: 2,
  },
  avatar: {
    ...original.avatar,
  },
};

console.log(watcher.isChanged(originalData, sneakyDifferentData)); // true

Multi object comparison

import { watchAll } from '@indutny/sneequals';

const inputA = { a: 1 };
const inputB = { b: 2 };

const { proxies, watcher } = watchAll([inputA, inputB]);

function fn(a, b) {
  return a.a + a.b;
}

const result = watcher.unwrap(fn(...proxies));

// Prevent further access to proxies
watcher.stop();

console.log(watcher.isChanged(inputA, { a: 1 })); // false
console.log(watcher.isChanged(inputB, { b: 3 })); // true

Memoization

memoize() is provided as a convenience API method. It has a simple WeakMap-based cache that keys by first object argument of the function and/or global internal key.

import { memoize } from '@indutny/sneequals';

const fn = memoize((a, b) => {
  return a.a + a.b;
});

Benchmarks

On M1 Macbook Pro 13:

$ npm run bench
watch+unwrap: 554431.062 operations/second
isChanged: 4575487.253 operations/second
memoize: 4070533.538 operations/second

Credits

Name coined by Scott Nonnenberg.

LICENSE

This software is licensed under the MIT License.