Implement a function deepEqual that performs a deep comparison between two values. It returns true if the two input values are deemed equal and false otherwise.

• Inputs are limited to undefined, numbers, strings, booleans, null, arrays, and plain objects.
• Arrays may be sparse. Their length and present indices are part of the structure being compared.
• There will not be cyclic objects, i.e. objects with circular references.

Examples

deepEqual('foo', 'foo'); // true
deepEqual({ id: 1 }, { id: 1 }); // true
deepEqual([1, 2, 3], [1, 2, 3]); // true
deepEqual([{ id: '1' }], [{ id: '2' }]); // false