JewelsAndStones.js

// Source : https://leetcode.com/problems/jewels-and-stones
// Author : Dean Shi
// Date   : 2018-01-29

/***************************************************************************************
 *
 * You're given strings J representing the types of stones that are jewels, and S
 * representing the stones you have.  Each character in S is a type of stone you have.
 * You want to know how many of the stones you have are also jewels.
 *
 * The letters in J are guaranteed distinct, and all characters in J and S are letters.
 * Letters are case sensitive, so "a" is considered a different type of stone from "A".
 *
 * Example 1:
 *
 * Input: J = "aA", S = "aAAbbbb"
 * Output: 3
 *
 * Example 2:
 *
 * Input: J = "z", S = "ZZ"
 * Output: 0
 *
 * Note:
 *
 * S and J will consist of letters and have length at most 50.
 * The characters in J are distinct.
 *
 ***************************************************************************************/

/**
 * @param {string} J
 * @param {string} S
 * @return {number}
 */
var numJewelsInStones = function(J, S) {
  const jSet = new Set(J)

  let result = 0
  for (let s of S) if (jSet.has(s)) result++

  return result
};