Number of Equivalent Domino Pairs

In this lab, you will build a function that calculates the number of equivalent domino pairs. A pair of dominoes dominoes[i] = [a, b] is equivalent to dominoes[j] = [c, d] if and only if either (a == c and b == d) or (a == d and b == c). In other words, one domino can be rotated to be equal to another domino.

Your task is to create a function numEquivDominoPairs that takes an array of dominoes as input and returns the number of equivalent pairs (i, j) for which 0 <= i < j < dominoes.length and dominoes[i] is equivalent to dominoes[j].

Example 1:

const dominoes = [
  [1, 2],
  [2, 1],
  [3, 4],
  [5, 6],
];
console.log(numEquivDominoPairs(dominoes)); // Output: 1

Example 2:

const dominoes = [
  [1, 2],
  [1, 2],
  [1, 1],
  [1, 2],
  [2, 2],
];
console.log(numEquivDominoPairs(dominoes)); // Output: 3

Constraints:

• 1 <= dominoes.length <= 4 * 104
• dominoes[i].length == 2
• 1 <= dominoes[i][j] <= 9

Challenges

1. Export the function numEquivDominoPairs from index.js.
2. Implement the function numEquivDominoPairs such that it passes the given test cases and any additional tested cases.