For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt, and this page is available as Markdown at /reference/predicate/isEqualWith.md.
Install massaman

    isEqualWith es-toolkit

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

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

    Usage

    isEqualWith(a, b, areValuesEqual)

    Use isEqualWith when you need special comparison logic. If the custom function returns true or false, that result is used; if it returns undefined, the default comparison method is used. Useful for case-insensitive comparison, excluding specific properties, approximate value comparison, etc.

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

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

isEqualWith('Hello', 'hello', caseInsensitiveCompare); // true
isEqualWith({ name: 'Alice' }, { name: 'ALICE' }, caseInsensitiveCompare); // true

    Can also be used for approximate number comparison.

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

// Floating-point error tolerance comparison
const approximateCompare = (a, b) => {
  if (typeof a === 'number' && typeof b === 'number') {
    return Math.abs(a - b) < 0.01; // Treat differences under 0.01 as equal
  }
};

isEqualWith(0.1 + 0.2, 0.3, approximateCompare); // true
isEqualWith({ price: 10.01 }, { price: 10.02 }, approximateCompare); // true

    Useful when you want to ignore specific properties during comparison.

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

// Ignoring specific properties during comparison
const ignoreTimestamp = (a, b, property) => {
  if (property === 'timestamp') {
    return true; // Always treat timestamp property as equal
  }
};

const obj1 = { id: 1, name: 'Test', timestamp: 1000 };
const obj2 = { id: 1, name: 'Test', timestamp: 2000 };
isEqualWith(obj1, obj2, ignoreTimestamp); // true

    Can implement complex custom comparison logic.

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

const areValuesEqual = (a, b, property) => {
  // Ignore ID
  if (property === 'id') {
    return true;
  }

  // Compare name case-insensitively
  if (property === 'name' && typeof a === 'string' && typeof b === 'string') {
    return a.toLowerCase() === b.toLowerCase();
  }

  // Use default comparison for the rest
  return undefined;
};

const user1 = { id: 1, name: 'Alice', age: 25 };
const user2 = { id: 999, name: 'ALICE', age: 25 };
isEqualWith(user1, user2, areValuesEqual); // true

    Parameters

    aunknownrequired

    The first value to compare.

    bunknownrequired

    The second value to compare.

    areValuesEqual(x: any, y: any, property?: PropertyKey, xParent?: any, yParent?: any, stack?: Map<any, any>) => boolean | voidrequired

    A custom comparison function. If it returns true or false, that result is used; if it returns undefined, the default comparison method is used.

    Returns

    Returns true if the two values are equal according to the custom criteria, false otherwise.

    boolean
    Source: es-toolkit

    Re-exported verbatim from es-toolkit. Implementation, edge cases, and performance behavior are owned upstream. This page mirrors the documentation at the pinned version; the linked source is authoritative.