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index.js

/**
 * @param {number} n - integer (n >= 0)
 * @param {number} d - digit (0 <= d <= 9)
 * square all numbers k between 0 and n (0 <= k <= n)
 * count the number of digits d used in the k*k's
 
 * example
 *
 * n = 10
 * d = 1
 * the k*k's are 0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100
 * d of 1 appears in 1, 16, 81, 100
 * therefore, count is 4
 */ 
 


function numberDig (n, d) {
 return Array.apply(null, { length: n }).map(function (_, i) {
  return i * i
 }).filter(function () {
  return n.toString().includes(d)
 }).length
}

numberDig(10, 1) // 4