fast-equals
Version:
A blazing fast equality comparison, either shallow or deep
643 lines (638 loc) • 23.7 kB
JavaScript
const { getOwnPropertyNames, getOwnPropertySymbols } = Object;
// eslint-disable-next-line @typescript-eslint/unbound-method
const { hasOwnProperty } = Object.prototype;
/**
* Combine two comparators into a single comparators.
*/
function combineComparators(comparatorA, comparatorB) {
return function isEqual(a, b, state) {
return comparatorA(a, b, state) && comparatorB(a, b, state);
};
}
/**
* Wrap the provided `areItemsEqual` method to manage the circular state, allowing
* for circular references to be safely included in the comparison without creating
* stack overflows.
*/
function createIsCircular(areItemsEqual) {
return function isCircular(a, b, state) {
if (!a || !b || typeof a !== 'object' || typeof b !== 'object') {
return areItemsEqual(a, b, state);
}
const { cache } = state;
const cachedA = cache.get(a);
const cachedB = cache.get(b);
if (cachedA && cachedB) {
return cachedA === b && cachedB === a;
}
cache.set(a, b);
cache.set(b, a);
const result = areItemsEqual(a, b, state);
cache.delete(a);
cache.delete(b);
return result;
};
}
/**
* Get the `@@toStringTag` of the value, if it exists.
*/
function getShortTag(value) {
return value != null ? value[Symbol.toStringTag] : undefined;
}
/**
* Get the properties to strictly examine, which include both own properties that are
* not enumerable and symbol properties.
*/
function getStrictProperties(object) {
return getOwnPropertyNames(object).concat(getOwnPropertySymbols(object));
}
/**
* Whether the object contains the property passed as an own property.
*/
const hasOwn =
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
Object.hasOwn || ((object, property) => hasOwnProperty.call(object, property));
/**
* Whether the values passed are strictly equal or both NaN.
*/
function sameValueZeroEqual(a, b) {
return a === b || (!a && !b && a !== a && b !== b);
}
const PREACT_VNODE = '__v';
const PREACT_OWNER = '__o';
const REACT_OWNER = '_owner';
const { getOwnPropertyDescriptor, keys } = Object;
/**
* Whether the array buffers are equal in value.
*/
function areArrayBuffersEqual(a, b) {
return a.byteLength === b.byteLength && areTypedArraysEqual(new Uint8Array(a), new Uint8Array(b));
}
/**
* Whether the arrays are equal in value.
*/
function areArraysEqual(a, b, state) {
let index = a.length;
if (b.length !== index) {
return false;
}
while (index-- > 0) {
if (!state.equals(a[index], b[index], index, index, a, b, state)) {
return false;
}
}
return true;
}
/**
* Whether the dataviews are equal in value.
*/
function areDataViewsEqual(a, b) {
return (a.byteLength === b.byteLength
&& areTypedArraysEqual(new Uint8Array(a.buffer, a.byteOffset, a.byteLength), new Uint8Array(b.buffer, b.byteOffset, b.byteLength)));
}
/**
* Whether the dates passed are equal in value.
*/
function areDatesEqual(a, b) {
return sameValueZeroEqual(a.getTime(), b.getTime());
}
/**
* Whether the errors passed are equal in value.
*/
function areErrorsEqual(a, b) {
return a.name === b.name && a.message === b.message && a.cause === b.cause && a.stack === b.stack;
}
/**
* Whether the functions passed are equal in value.
*/
function areFunctionsEqual(a, b) {
return a === b;
}
/**
* Whether the `Map`s are equal in value.
*/
function areMapsEqual(a, b, state) {
const size = a.size;
if (size !== b.size) {
return false;
}
if (!size) {
return true;
}
const matchedIndices = new Array(size);
const aIterable = a.entries();
let aResult;
let bResult;
let index = 0;
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
while ((aResult = aIterable.next())) {
if (aResult.done) {
break;
}
const bIterable = b.entries();
let hasMatch = false;
let matchIndex = 0;
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
while ((bResult = bIterable.next())) {
if (bResult.done) {
break;
}
if (matchedIndices[matchIndex]) {
matchIndex++;
continue;
}
const aEntry = aResult.value;
const bEntry = bResult.value;
if (state.equals(aEntry[0], bEntry[0], index, matchIndex, a, b, state)
&& state.equals(aEntry[1], bEntry[1], aEntry[0], bEntry[0], a, b, state)) {
hasMatch = matchedIndices[matchIndex] = true;
break;
}
matchIndex++;
}
if (!hasMatch) {
return false;
}
index++;
}
return true;
}
/**
* Whether the numbers are equal in value.
*/
const areNumbersEqual = sameValueZeroEqual;
/**
* Whether the objects are equal in value.
*/
function areObjectsEqual(a, b, state) {
const properties = keys(a);
let index = properties.length;
if (keys(b).length !== index) {
return false;
}
// Decrementing `while` showed faster results than either incrementing or
// decrementing `for` loop and than an incrementing `while` loop. Declarative
// methods like `some` / `every` were not used to avoid incurring the garbage
// cost of anonymous callbacks.
while (index-- > 0) {
if (!isPropertyEqual(a, b, state, properties[index])) {
return false;
}
}
return true;
}
/**
* Whether the objects are equal in value with strict property checking.
*/
function areObjectsEqualStrict(a, b, state) {
const properties = getStrictProperties(a);
let index = properties.length;
if (getStrictProperties(b).length !== index) {
return false;
}
let property;
let descriptorA;
let descriptorB;
// Decrementing `while` showed faster results than either incrementing or
// decrementing `for` loop and than an incrementing `while` loop. Declarative
// methods like `some` / `every` were not used to avoid incurring the garbage
// cost of anonymous callbacks.
while (index-- > 0) {
property = properties[index];
if (!isPropertyEqual(a, b, state, property)) {
return false;
}
descriptorA = getOwnPropertyDescriptor(a, property);
descriptorB = getOwnPropertyDescriptor(b, property);
if ((descriptorA || descriptorB)
&& (!descriptorA
|| !descriptorB
|| descriptorA.configurable !== descriptorB.configurable
|| descriptorA.enumerable !== descriptorB.enumerable
|| descriptorA.writable !== descriptorB.writable)) {
return false;
}
}
return true;
}
/**
* Whether the primitive wrappers passed are equal in value.
*/
function arePrimitiveWrappersEqual(a, b) {
return sameValueZeroEqual(a.valueOf(), b.valueOf());
}
/**
* Whether the regexps passed are equal in value.
*/
function areRegExpsEqual(a, b) {
return a.source === b.source && a.flags === b.flags;
}
/**
* Whether the `Set`s are equal in value.
*/
function areSetsEqual(a, b, state) {
const size = a.size;
if (size !== b.size) {
return false;
}
if (!size) {
return true;
}
const matchedIndices = new Array(size);
const aIterable = a.values();
let aResult;
let bResult;
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
while ((aResult = aIterable.next())) {
if (aResult.done) {
break;
}
const bIterable = b.values();
let hasMatch = false;
let matchIndex = 0;
// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
while ((bResult = bIterable.next())) {
if (bResult.done) {
break;
}
if (!matchedIndices[matchIndex]
&& state.equals(aResult.value, bResult.value, aResult.value, bResult.value, a, b, state)) {
hasMatch = matchedIndices[matchIndex] = true;
break;
}
matchIndex++;
}
if (!hasMatch) {
return false;
}
}
return true;
}
/**
* Whether the TypedArray instances are equal in value.
*/
function areTypedArraysEqual(a, b) {
let index = a.byteLength;
if (b.byteLength !== index || a.byteOffset !== b.byteOffset) {
return false;
}
while (index-- > 0) {
if (a[index] !== b[index]) {
return false;
}
}
return true;
}
/**
* Whether the URL instances are equal in value.
*/
function areUrlsEqual(a, b) {
return (a.hostname === b.hostname
&& a.pathname === b.pathname
&& a.protocol === b.protocol
&& a.port === b.port
&& a.hash === b.hash
&& a.username === b.username
&& a.password === b.password);
}
function isPropertyEqual(a, b, state, property) {
if ((property === REACT_OWNER || property === PREACT_OWNER || property === PREACT_VNODE)
&& (a.$$typeof || b.$$typeof)) {
return true;
}
return hasOwn(b, property) && state.equals(a[property], b[property], property, property, a, b, state);
}
const ARRAY_BUFFER_TAG = '[object ArrayBuffer]';
const ARGUMENTS_TAG = '[object Arguments]';
const BOOLEAN_TAG = '[object Boolean]';
const DATA_VIEW_TAG = '[object DataView]';
const DATE_TAG = '[object Date]';
const ERROR_TAG = '[object Error]';
const MAP_TAG = '[object Map]';
const NUMBER_TAG = '[object Number]';
const OBJECT_TAG = '[object Object]';
const REG_EXP_TAG = '[object RegExp]';
const SET_TAG = '[object Set]';
const STRING_TAG = '[object String]';
const TYPED_ARRAY_TAGS = {
'[object Int8Array]': true,
'[object Uint8Array]': true,
'[object Uint8ClampedArray]': true,
'[object Int16Array]': true,
'[object Uint16Array]': true,
'[object Int32Array]': true,
'[object Uint32Array]': true,
'[object Float16Array]': true,
'[object Float32Array]': true,
'[object Float64Array]': true,
'[object BigInt64Array]': true,
'[object BigUint64Array]': true,
};
const URL_TAG = '[object URL]';
// eslint-disable-next-line @typescript-eslint/unbound-method
const toString = Object.prototype.toString;
/**
* Create a comparator method based on the type-specific equality comparators passed.
*/
function createEqualityComparator({ areArrayBuffersEqual, areArraysEqual, areDataViewsEqual, areDatesEqual, areErrorsEqual, areFunctionsEqual, areMapsEqual, areNumbersEqual, areObjectsEqual, arePrimitiveWrappersEqual, areRegExpsEqual, areSetsEqual, areTypedArraysEqual, areUrlsEqual, unknownTagComparators, }) {
/**
* compare the value of the two objects and return true if they are equivalent in values
*/
return function comparator(a, b, state) {
// If the items are strictly equal, no need to do a value comparison.
if (a === b) {
return true;
}
// If either of the items are nullish and fail the strictly equal check
// above, then they must be unequal.
if (a == null || b == null) {
return false;
}
const type = typeof a;
if (type !== typeof b) {
return false;
}
if (type !== 'object') {
if (type === 'number') {
return areNumbersEqual(a, b, state);
}
if (type === 'function') {
return areFunctionsEqual(a, b, state);
}
// If a primitive value that is not strictly equal, it must be unequal.
return false;
}
const constructor = a.constructor;
// Checks are listed in order of commonality of use-case:
// 1. Common complex object types (plain object, array)
// 2. Common data values (date, regexp)
// 3. Less-common complex object types (map, set)
// 4. Less-common data values (promise, primitive wrappers)
// Inherently this is both subjective and assumptive, however
// when reviewing comparable libraries in the wild this order
// appears to be generally consistent.
// Constructors should match, otherwise there is potential for false positives
// between class and subclass or custom object and POJO.
if (constructor !== b.constructor) {
return false;
}
// `isPlainObject` only checks against the object's own realm. Cross-realm
// comparisons are rare, and will be handled in the ultimate fallback, so
// we can avoid capturing the string tag.
if (constructor === Object) {
return areObjectsEqual(a, b, state);
}
// `isArray()` works on subclasses and is cross-realm, so we can avoid capturing
// the string tag or doing an `instanceof` check.
if (Array.isArray(a)) {
return areArraysEqual(a, b, state);
}
// Try to fast-path equality checks for other complex object types in the
// same realm to avoid capturing the string tag. Strict equality is used
// instead of `instanceof` because it is more performant for the common
// use-case. If someone is subclassing a native class, it will be handled
// with the string tag comparison.
if (constructor === Date) {
return areDatesEqual(a, b, state);
}
if (constructor === RegExp) {
return areRegExpsEqual(a, b, state);
}
if (constructor === Map) {
return areMapsEqual(a, b, state);
}
if (constructor === Set) {
return areSetsEqual(a, b, state);
}
// Since this is a custom object, capture the string tag to determing its type.
// This is reasonably performant in modern environments like v8 and SpiderMonkey.
const tag = toString.call(a);
if (tag === DATE_TAG) {
return areDatesEqual(a, b, state);
}
// For RegExp, the properties are not enumerable, and therefore will give false positives if
// tested like a standard object.
if (tag === REG_EXP_TAG) {
return areRegExpsEqual(a, b, state);
}
if (tag === MAP_TAG) {
return areMapsEqual(a, b, state);
}
if (tag === SET_TAG) {
return areSetsEqual(a, b, state);
}
if (tag === OBJECT_TAG) {
// The exception for value comparison is custom `Promise`-like class instances. These should
// be treated the same as standard `Promise` objects, which means strict equality, and if
// it reaches this point then that strict equality comparison has already failed.
return typeof a.then !== 'function' && typeof b.then !== 'function' && areObjectsEqual(a, b, state);
}
// If a URL tag, it should be tested explicitly. Like RegExp, the properties are not
// enumerable, and therefore will give false positives if tested like a standard object.
if (tag === URL_TAG) {
return areUrlsEqual(a, b, state);
}
// If an error tag, it should be tested explicitly. Like RegExp, the properties are not
// enumerable, and therefore will give false positives if tested like a standard object.
if (tag === ERROR_TAG) {
return areErrorsEqual(a, b, state);
}
// If an arguments tag, it should be treated as a standard object.
if (tag === ARGUMENTS_TAG) {
return areObjectsEqual(a, b, state);
}
if (TYPED_ARRAY_TAGS[tag]) {
return areTypedArraysEqual(a, b, state);
}
if (tag === ARRAY_BUFFER_TAG) {
return areArrayBuffersEqual(a, b, state);
}
if (tag === DATA_VIEW_TAG) {
return areDataViewsEqual(a, b, state);
}
// As the penultimate fallback, check if the values passed are primitive wrappers. This
// is very rare in modern JS, which is why it is deprioritized compared to all other object
// types.
if (tag === BOOLEAN_TAG || tag === NUMBER_TAG || tag === STRING_TAG) {
return arePrimitiveWrappersEqual(a, b, state);
}
if (unknownTagComparators) {
let unknownTagComparator = unknownTagComparators[tag];
if (!unknownTagComparator) {
const shortTag = getShortTag(a);
if (shortTag) {
unknownTagComparator = unknownTagComparators[shortTag];
}
}
// If the custom config has an unknown tag comparator that matches the captured tag or the
// @@toStringTag, it is the source of truth for whether the values are equal.
if (unknownTagComparator) {
return unknownTagComparator(a, b, state);
}
}
// If not matching any tags that require a specific type of comparison, then we hard-code false because
// the only thing remaining is strict equality, which has already been compared. This is for a few reasons:
// - Certain types that cannot be introspected (e.g., `WeakMap`). For these types, this is the only
// comparison that can be made.
// - For types that can be introspected, but rarely have requirements to be compared
// (`ArrayBuffer`, `DataView`, etc.), the cost is avoided to prioritize the common
// use-cases (may be included in a future release, if requested enough).
// - For types that can be introspected but do not have an objective definition of what
// equality is (`Error`, etc.), the subjective decision is to be conservative and strictly compare.
// In all cases, these decisions should be reevaluated based on changes to the language and
// common development practices.
return false;
};
}
/**
* Create the configuration object used for building comparators.
*/
function createEqualityComparatorConfig({ circular, createCustomConfig, strict, }) {
let config = {
areArrayBuffersEqual,
areArraysEqual: strict ? areObjectsEqualStrict : areArraysEqual,
areDataViewsEqual,
areDatesEqual: areDatesEqual,
areErrorsEqual: areErrorsEqual,
areFunctionsEqual: areFunctionsEqual,
areMapsEqual: strict ? combineComparators(areMapsEqual, areObjectsEqualStrict) : areMapsEqual,
areNumbersEqual: areNumbersEqual,
areObjectsEqual: strict ? areObjectsEqualStrict : areObjectsEqual,
arePrimitiveWrappersEqual: arePrimitiveWrappersEqual,
areRegExpsEqual: areRegExpsEqual,
areSetsEqual: strict ? combineComparators(areSetsEqual, areObjectsEqualStrict) : areSetsEqual,
areTypedArraysEqual: strict
? combineComparators(areTypedArraysEqual, areObjectsEqualStrict)
: areTypedArraysEqual,
areUrlsEqual: areUrlsEqual,
unknownTagComparators: undefined,
};
if (createCustomConfig) {
config = Object.assign({}, config, createCustomConfig(config));
}
if (circular) {
const areArraysEqual = createIsCircular(config.areArraysEqual);
const areMapsEqual = createIsCircular(config.areMapsEqual);
const areObjectsEqual = createIsCircular(config.areObjectsEqual);
const areSetsEqual = createIsCircular(config.areSetsEqual);
config = Object.assign({}, config, {
areArraysEqual,
areMapsEqual,
areObjectsEqual,
areSetsEqual,
});
}
return config;
}
/**
* Default equality comparator pass-through, used as the standard `isEqual` creator for
* use inside the built comparator.
*/
function createInternalEqualityComparator(compare) {
return function (a, b, _indexOrKeyA, _indexOrKeyB, _parentA, _parentB, state) {
return compare(a, b, state);
};
}
/**
* Create the `isEqual` function used by the consuming application.
*/
function createIsEqual({ circular, comparator, createState, equals, strict }) {
if (createState) {
return function isEqual(a, b) {
const { cache = circular ? new WeakMap() : undefined, meta } = createState();
return comparator(a, b, {
cache,
equals,
meta,
strict,
});
};
}
if (circular) {
return function isEqual(a, b) {
return comparator(a, b, {
cache: new WeakMap(),
equals,
meta: undefined,
strict,
});
};
}
const state = {
cache: undefined,
equals,
meta: undefined,
strict,
};
return function isEqual(a, b) {
return comparator(a, b, state);
};
}
/**
* Whether the items passed are deeply-equal in value.
*/
const deepEqual = createCustomEqual();
/**
* Whether the items passed are deeply-equal in value based on strict comparison.
*/
const strictDeepEqual = createCustomEqual({ strict: true });
/**
* Whether the items passed are deeply-equal in value, including circular references.
*/
const circularDeepEqual = createCustomEqual({ circular: true });
/**
* Whether the items passed are deeply-equal in value, including circular references,
* based on strict comparison.
*/
const strictCircularDeepEqual = createCustomEqual({
circular: true,
strict: true,
});
/**
* Whether the items passed are shallowly-equal in value.
*/
const shallowEqual = createCustomEqual({
createInternalComparator: () => sameValueZeroEqual,
});
/**
* Whether the items passed are shallowly-equal in value based on strict comparison
*/
const strictShallowEqual = createCustomEqual({
strict: true,
createInternalComparator: () => sameValueZeroEqual,
});
/**
* Whether the items passed are shallowly-equal in value, including circular references.
*/
const circularShallowEqual = createCustomEqual({
circular: true,
createInternalComparator: () => sameValueZeroEqual,
});
/**
* Whether the items passed are shallowly-equal in value, including circular references,
* based on strict comparison.
*/
const strictCircularShallowEqual = createCustomEqual({
circular: true,
createInternalComparator: () => sameValueZeroEqual,
strict: true,
});
/**
* Create a custom equality comparison method.
*
* This can be done to create very targeted comparisons in extreme hot-path scenarios
* where the standard methods are not performant enough, but can also be used to provide
* support for legacy environments that do not support expected features like
* `RegExp.prototype.flags` out of the box.
*/
function createCustomEqual(options = {}) {
const { circular = false, createInternalComparator: createCustomInternalComparator, createState, strict = false, } = options;
const config = createEqualityComparatorConfig(options);
const comparator = createEqualityComparator(config);
const equals = createCustomInternalComparator
? createCustomInternalComparator(comparator)
: createInternalEqualityComparator(comparator);
return createIsEqual({ circular, comparator, createState, equals, strict });
}
export { circularDeepEqual, circularShallowEqual, createCustomEqual, deepEqual, sameValueZeroEqual, shallowEqual, strictCircularDeepEqual, strictCircularShallowEqual, strictDeepEqual, strictShallowEqual };
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