doocs/leetcode · error · Error

Not Equal

Error message

Not Equal

What it means

This error is thrown by a hand-rolled expect(val).toBe(expected) assertion helper for LeetCode problem 2704. It uses strict equality (!==), so toBe rejects any pair that is not strictly equal, including cases where == would pass such as 1 vs '1' or two objects with identical contents. The thrown Error('Not Equal') is the expected output the judge captures via expect(() => ...).toThrow().

Source

Thrown at solution/2700-2799/2704.To Be Or Not To Be/Solution.js:9

/**
 * @param {string} val
 * @return {Object}
 */
var expect = function (val) {
    return {
        toBe: function (expected) {
            if (val !== expected) {
                throw new Error('Not Equal');
            }
            return true;
        },
        notToBe: function (expected) {
            if (val === expected) {
                throw new Error('Equal');
            }
            return true;
        },
    };
};

/**
 * expect(5).toBe(5); // true
 * expect(5).notToBe(5); // throws "Equal"
 */

View on GitHub (pinned to f84f361dc4)

Solutions

1. Confirm the mismatch is intended: toBe is strict (===) equality, so '5' vs 5 or two separately-created objects are correctly 'Not Equal'
2. If you expected deep equality, compare JSON.stringify(val) === JSON.stringify(expected) or use a deep-equal helper instead
3. Use notToBe when you want the assertion to pass on unequal values
4. Wrap the call in expect(() => fn()).toThrow('Not Equal') when testing the thrower itself

Example fix

// before
expect('5').toBe(5); // throws 'Not Equal'

// after
expect(Number('5')).toBe(5); // passes
// or assert the throw:
jest.fn(() => expect('5').toBe(5)); // toThrow('Not Equal')

if (val === expected) { /* toBe will pass */ } else { /* toBe will throw 'Not Equal' */ }

const isStrictlyEqual = (a: unknown, b: unknown): boolean => a === b;

try { expect(5).toBe(x); } catch (e) { if ((e as Error).message !== 'Not Equal') throw e; /* handle mismatch */ }

When it happens

Trigger: Calling expect(5).toBe('5') (type mismatch under ===), expect({}).toBe({}) (different object identities), or any value/expected pair that fails strict equality.

Common situations: Writing or testing the assertion utility itself; confusing === with ==; expecting toBe to behave like deep equality (e.g. comparing objects or arrays); accidentally comparing NaN (NaN !== NaN always throws here).

Related errors

• Equal
• Not Equal
• Equal
• Not Equal
• Equal

AI-assisted analysis of doocs/leetcode@f84f361dc4 (2026-08-27). Data as JSON: /api/errors/7b7949e8603bf7b6. Report an issue: GitHub.