Function isProperSubsetOf

Implementation of the proper subset operation, which checks if set A is a proper subset of set B. A proper subset means a set A is a subset of B, but is not equal to B.

• Formal definition: A ⊂ B
• This method runs in bilinear time, or O(n * m), where n = |A| (size of set A), and m = |B| (set of size B)

Example

// {1} ⊂ {1, 3}
isProperSubsetOf(new Set([1]), new Set([1, 3])); // true
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