add ability to override number comparisons

__tests__/comparator.ts

@@ -15,7 +15,7 @@ import {
   areTypedArraysEqual,
   areUrlsEqual,
 } from '../src/equals';
-import { createIsCircular } from '../src/utils';
+import { createIsCircular, sameValueZeroEqual } from '../src/utils';
 
 import type { InternalEqualityComparator, State } from '../src/internalTypes';
 
@@ -25,6 +25,7 @@ const STANDARD_COMPARATOR_OPTIONS = {
   areErrorsEqual,
   areFunctionsEqual,
   areMapsEqual,
+  areNumbersEqual: sameValueZeroEqual,
   areObjectsEqual,
   arePrimitiveWrappersEqual,
   areRegExpsEqual,

__tests__/index.ts

@@ -453,6 +453,32 @@ describe('strict', () => {
       expect(customEqual(a, b)).toBe(false);
     });
 
+    it('issue 112 - handle custom float comparison', () => {
+      const customEqual = createCustomEqual({
+        createCustomConfig: () => ({
+          areNumbersEqual(a, b) {
+            if (a === b) {
+              return true;
+            }
+
+            const diff = Math.abs(a - b);
+
+            if (diff < Number.EPSILON) {
+              return true;
+            }
+
+            return diff <= Number.EPSILON * Math.min(Math.abs(a), Math.abs(b));
+          },
+        }),
+      });
+
+      const a = 0.1 + 0.2;
+      const b = 0.3;
+
+      expect(deepEqual(a, b)).toBe(false);
+      expect(customEqual(a, b)).toBe(true);
+    });
+
     it('issue 123 - custom function equality comparator', () => {
       const customEqual = createCustomEqual({
         createCustomConfig: () => ({

src/comparator.ts

@@ -4,6 +4,7 @@ import {
   areErrorsEqual as areErrorsEqualDefault,
   areFunctionsEqual as areFunctionsEqualDefault,
   areMapsEqual as areMapsEqualDefault,
+  areNumbersEqual as areNumbersEqualDefault,
   areObjectsEqual as areObjectsEqualDefault,
   areObjectsEqualStrict as areObjectsEqualStrictDefault,
   arePrimitiveWrappersEqual as arePrimitiveWrappersEqualDefault,
@@ -61,6 +62,7 @@ export function createEqualityComparator<Meta>({
   areErrorsEqual,
   areFunctionsEqual,
   areMapsEqual,
+  areNumbersEqual,
   areObjectsEqual,
   arePrimitiveWrappersEqual,
   areRegExpsEqual,
@@ -91,10 +93,7 @@ export function createEqualityComparator<Meta>({
 
     if (type !== 'object') {
       if (type === 'number') {
-        // If the items are numbers, then the only possibility of them being equal but not strictly is if they are both
-        // `NaN`. Since `NaN` is uniquely not equal to itself, we can use self-comparison of both objects, which is
-        // faster than `isNaN()`.
-        return a !== a && b !== b;
+        return areNumbersEqual(a, b, state);
       }
 
       if (type === 'function') {
@@ -253,6 +252,7 @@ export function createEqualityComparatorConfig<Meta>({
     areMapsEqual: strict
       ? combineComparators(areMapsEqualDefault, areObjectsEqualStrictDefault)
       : areMapsEqualDefault,
+    areNumbersEqual: areNumbersEqualDefault,
     areObjectsEqual: strict
       ? areObjectsEqualStrictDefault
       : areObjectsEqualDefault,

src/equals.ts

@@ -118,6 +118,11 @@ export function areMapsEqual(
   return true;
 }
 
+/**
+ * Whether the numbers are equal in value.
+ */
+export const areNumbersEqual = sameValueZeroEqual;
+
 /**
  * Whether the objects are equal in value.
  */

src/internalTypes.ts

@@ -65,6 +65,10 @@ export interface ComparatorConfig<Meta> {
    * additional properties added to the map.
    */
   areMapsEqual: TypeEqualityComparator<any, Meta>;
+  /**
+   * Whether the numbers passed are equal in value.
+   */
+  areNumbersEqual: TypeEqualityComparator<any, Meta>;
   /**
    * Whether the objects passed are equal in value. In strict mode, this includes
    * non-enumerable properties added to the map, as well as symbol properties.

src/utils.ts

@@ -84,5 +84,5 @@ export const hasOwn =
  * Whether the values passed are strictly equal or both NaN.
  */
 export function sameValueZeroEqual(a: any, b: any): boolean {
-  return a || b ? a === b : a === b || (a !== a && b !== b);
+  return a === b || (!a && !b && a !== a && b !== b);
 }