isEqualWith (Lodash Compatibility)

::: warning Use es-toolkit's isEqualWith instead This isEqualWith function operates slowly due to complex processing for Lodash compatibility.

Use the faster and more modern es-toolkit's isEqualWith instead. :::

Checks if two values are equal using a custom comparison function.

const result = isEqualWith(a, b, customizer);

Usage

isEqualWith(a, b, areValuesEqual?)

Deeply compares two values using a custom comparison function. If the custom function returns a boolean value, that result is used. If it returns undefined, the default equality comparison is used.

The custom comparison function is also used when comparing values inside complex structures like objects, arrays, Map, Set, etc., ensuring deep comparison.

import { isEqualWith } from 'es-toolkit/compat';

// Case-insensitive string comparison
const customizer = (a: any, b: any) => {
  if (typeof a === 'string' && typeof b === 'string') {
    return a.toLowerCase() === b.toLowerCase();
  }
};

isEqualWith('Hello', 'hello', customizer); // true
isEqualWith({ a: 'Hello' }, { a: 'hello' }, customizer); // true

// Compare numbers by absolute value
const absCustomizer = (a: any, b: any) => {
  if (typeof a === 'number' && typeof b === 'number') {
    return Math.abs(a) === Math.abs(b);
  }
};

isEqualWith([-1, 2], [1, -2], absCustomizer); // true

// Complex object comparison
const obj1 = {
  name: 'JOHN',
  details: { age: 30, city: 'NYC' },
};
const obj2 = {
  name: 'john',
  details: { age: 30, city: 'nyc' },
};

isEqualWith(obj1, obj2, customizer); // true

Special handling for Map and Set:

import { isEqualWith } from 'es-toolkit/compat';

const customizer = (a: any, b: any) => {
  if (typeof a === 'string' && typeof b === 'string') {
    return a.toLowerCase() === b.toLowerCase();
  }
};

const map1 = new Map([['KEY', 'value']]);
const map2 = new Map([['key', 'value']]);
isEqualWith(map1, map2, customizer); // true

const set1 = new Set(['HELLO']);
const set2 = new Set(['hello']);
isEqualWith(set1, set2, customizer); // true

Parameters

• a (any): The first value to compare.
• b (any): The second value to compare.
• areValuesEqual ((x: any, y: any, property?: PropertyKey, xParent?: any, yParent?: any, stack?: Map<any, any>) => boolean | void): The custom comparison function.
  • x: Value from the first object a
  • y: Value from the second object b
  • property: The property key used to get x and y
  • xParent: The parent object of the first value x
  • yParent: The parent object of the second value y
  • stack: Internal stack (Map) for handling circular references

Returns

(boolean): Returns true if the values are equal according to the custom function, false otherwise.