# fast-equals CHANGELOG

## 5.0.1

### Bugfixes

- Fix reference to `metaOverride` in typings and documentation (holdover from temporary API in v5 beta)

## 5.0.0

### Breaking changes

#### `constructor` equality now required

To align with other implementations common in the community, but also to be more functionally correct, the two objects being compared now must have equal `constructor`s.

#### `Map` / `Set` comparisons no longer support IE11

In previous verisons, `.forEach()` was used to ensure that support for `Symbol` was not required, as IE11 did not have `Symbol` and therefore both `Map` and `Set` did not have iterator-based methods such as `.values()` or `.entries()`. Since IE11 is no longer a supported browser, and support for those methods is present in all browsers and Node for quite a while, the comparison has moved to use these methods. This results in a ~20% performance increase.

#### `createCustomEqual` contract has changed

To better facilitate strict comparisons, but also to allow for `meta` use separate from caching, the contract for `createCustomEqual` has changed. See the [README documentation](./README.md#createcustomequal) for more details, but froma high-level:

- `meta` is no longer passed through to equality comparators, but rather a general `state` object which contains `meta`
- `cache` now also lives on the `state` object, which allows for use of the `meta` property separate from but in parallel with the circular cache
- `equals` is now on `state`, which prevents the need to pass through the separate `isEqual` method for the equality comparator

#### `createCustomCircularEqual` has been removed

You can create a custom circular equality comparator through `createCustomEqual` now by providing `circular: true` to the options.

#### Custom `meta` values are no longer passed at callsite

To use `meta` properties for comparisons, they must be returned in a `createState` method.

#### Deep links have changed

If you were deep-linking into a specific asset type (ESM / CJS / UMD), they have changed location.

**NOTE**: You may no longer need to deep-link, as [the build resolution has improved](#better-build-system-resolution).

### Enhancements

#### New "strict" comparators available

The following new comparators are available:

- `strictDeepEqual`
- `strictShallowEqual`
- `strictCircularDeepEqual`
- `strictCircularShallowEqual`

This will perform the same comparisons as their non-strict counterparts, but will verify additional properties (non-enumerable properties on objects, keyed objects on `Array` / `Map` / `Set`) and that the descriptors for the properties align.

#### `TypedArray` support

Support for comparing all typed array values is now supported, and you can provide a custom comparator via the new `areTypedArraysEqual` option in the `createCustomEqual` configuration.

#### Better build system resolution

The library now leverages the `exports` property in the `package.json` to provide builds specific to your method of consumption (ESM / CommonJS / UMD). There is still a minified UMD version available if you want to use it instead.

#### `arePrimitiveWrappersEqual` option added to `createCustomEqual` configuration

If you want a custom comparator for primitive wrappers (`new Boolean()` / `new Number()` / `new String()`) it is now available.

## 4.0.3

- Remove unnecessary second strict equality check for objects in edge-case scenarios

## 4.0.2

- [#85](https://github.com/planttheidea/fast-equals/issues/85) - `createCustomCircularEqual` typing is incorrect

## 4.0.1

- [#81](https://github.com/planttheidea/fast-equals/issues/81) - Fix typing issues related to importing in `index.d.ts` file

## 4.0.0

### Breaking Changes

#### Certain ES2015 features are now required

In previous versions, there were automatic fallbacks for certain ES2015 features if they did not exist:

- [`RegExp.prototype.flags`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/flags)
- [`WeakMap`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap)

Due to the omnipresence of support in both browser and NodeJS, these have been deprecated. There is still an option if you require support for these legacy environments, however; see [`createCustomEqual`](./README.md#createcustomequal) and [`createCustomCircularEqual`](./README.md#createcustomcircularequal) for more details.

#### `createCustomEqual` contract has changed

To allow more flexibility and customizability for a variety of edge cases, `createCustomEqual` now allows override of specific type value comparisons in addition to the general comparator it did prior. See [the documentation](./README.md#createcustomequal) for more details.

### Enhancements

#### `createCustomCircularEqual` added

Like `createCustomEqual`, it will create a custom equality comparator, with the exception that it will handle circular references. See [the documentation](./README.md#createcustomcircularequal) for more details.

#### Cross-realm comparisons are now supported

Prior to `4.x.x.`, `instanceof` was used internally for checking of object classes, which only worked when comparing objects from the same [Realm](https://262.ecma-international.org/6.0/#sec-code-realms). This has changed to instead use an object's [StringTag](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol/toStringTag), which is not realm-specific.

#### TypeScript typings improved

For better typing in edge-case scenarios like custom comparators with `meta` values, typings have been refactored for accuracy and better narrow flow-through.

## 3.0.3

- Fix [#77](https://github.com/planttheidea/fast-equals/issues/73) - better circular object validation

## 3.0.2

- Fix [#73](https://github.com/planttheidea/fast-equals/issues/73) - support comparison of primitive wrappers
- [#76](https://github.com/planttheidea/fast-equals/pull/76) - improve speed and accuracy of `RegExp` comparison in modern environments

## 3.0.1

- Fix [#71](https://github.com/planttheidea/fast-equals/pull/71) - use generic types for better type flow-through

## 3.0.0

### Breaking changes

When creating a custom equality comparator via `createCustomEqual`, the equality method has an expanded contract:

```ts
// Before
type EqualityComparator = (objectA: any, objectB: any, meta: any) => boolean;

// After
type InternalEqualityComparator = (
  objectA: any,
  objectB: any,
  indexOrKeyA: any,
  indexOrKeyB: any,
  parentA: any,
  parentB: any,
  meta: any,
) => boolean;
```

If you have a custom equality comparator, you can ignore the differences by just passing additional `undefined` parameters, or you can use the parameters to further improve / clarify the logic.

- Add [#57](https://github.com/planttheidea/fast-equals/pull/57) - support additional metadata for custom equality comparators

## 2.0.4

- Fix [#58](https://github.com/planttheidea/fast-equals/issues/58) - duplicate entries in `Map` / `Set` can create false equality success
- [#60](https://github.com/planttheidea/fast-equals/issues/60) - Add documentation for key equality of `Map` being a part of `deepEqual`

## 2.0.3

- Fix [#50](https://github.com/planttheidea/fast-equals/pull/50) - copy-pasta in cacheable check

## 2.0.2

- Optimize iterables comparisons to not double-iterate
- Optimize loop-based comparisons for speed
- Improve cache handling in circular handlers
- Improve stability of memory by reducing variable instantiation

## 2.0.1

- Fix [#41](https://github.com/planttheidea/fast-equals/pull/41) - prevent `.rpt2_cache` directory from being published for better CI environment support (thanks [@herberttn](https://github.com/herberttn))

## 2.0.0

### Breaking changes

- There are longer `fast-equals/es`, `fast-equals/lib`, `fast-equals/mjs` locations
  - Instead, there are 3 builds in `dist` for different consumption types:
    - `fast-equals.js` (UMD / `browser`)
    - `fast-equals.esm.js` (ESM / `module`)
    - `fast-equals.cjs.js` (CommonJS / `main`)
- There is no default export anymore, only the previously-existing named exports
  - To get all into a namespace, use `import * as fe from 'fast-equals`

### Updates

- Rewritten completely in TypeScript
- Improve speed of `Map` / `Set` comparisons
- Improve speed of React element comparisons

### Fixes

- Consider pure objects (`Object.create(null)`) to be plain objects
- Fix typings for `createCustomEqual`

## 1.6.3

- Check the size of the iterable before converting to arrays

## 1.6.2

- Fix [#23](https://github.com/planttheidea/fast-equals/issues/23) - false positives for map
- Replace `uglify` with `terser`
- Use `rollup` to build all the distributables (`main`, `module`, and `browser`)
  - Maintain `lib` and `es` transpilations in case consumers were deep-linking

## 1.6.1

- Upgrade to `babel@7`
- Add `"sideEffects": false` to `package.json` for better tree-shaking in `webpack`

## 1.6.0

- Add ESM support for NodeJS with separate [`.mjs` extension](https://nodejs.org/api/esm.html) exports

## 1.5.3

- Fix `Map` / `Set` comparison to not require order to match to be equal

## 1.5.2

- Improve speed of object comparison through custom `hasKey` method

## 1.5.1

- Fix lack of support for `unicode` and `sticky` RegExp flag checks

## 1.5.0

- Add [`circularDeepEqual`](README.md#circulardeepequal) and [`circularShallowEqual`](README.md#circularshallowequal) methods
- Add `meta` third parameter to `comparator` calls, for use with `createCustomEqual` method

## 1.4.1

- Fix issue where `lastIndex` was not being tested on `RegExp` objects

## 1.4.0

- Add support for comparing promise-like objects (strict equality only)

## 1.3.1

- Make `react` comparison more accurate, and a touch faster

## 1.3.0

- Add support for deep-equal comparisons between `react` elements
- Add comparison with `react-fast-compare`
- Use `rollup` for `dist` file builds

## 1.2.1

- Fix errors from TypeScript typings in strict mode (thanks [@HitoriSensei](https://github.com/HitoriSensei))

## 1.2.0

- Surface `isSameValueZero` as [`sameValueZeroEqual`](#samevaluezeroequal) option

## 1.1.0

- Add TypeScript typings (thanks [@josh-sachs](https://github.com/josh-sachs))

## 1.0.6

- Support invalid date equality via `isSameValueZero`

## 1.0.5

- Replace `isStrictlyEqual` with `isSameValueZero` to ensure that `shallowEqual` accounts for `NaN` equality

## 1.0.4

- Only check values when comparing `Set` objects (improves performance of `Set` check by ~12%)

## 1.0.3

- Make `Map` and `Set` comparisons more explicit

## 1.0.2

- Fix symmetrical comparison of iterables
- Reduce footprint

## 1.0.1

- Prevent babel transpilation of `typeof` into helper for faster runtime

## 1.0.0

- Initial release

```

```