771 Jewels and Stones.js

/**
 * 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".
 * 给定字符串J 代表石头中宝石的类型，和字符串 S代表你拥有的石头。 S 中每个
 * 字符代表了一种你拥有的石头的类型，你想知道你拥有的石头中有多少是宝石。
 * J 中的字母不重复，J 和 S中的所有字符都是字母。字母区分大小写，因此"a"
 * 和"A"是不同类型的石头。
 */

/**
 * Example:
 * Input: J = "aA", S = "aAAbbbb"
 * Output: 3
 */

/**
 * @param {string} J
 * @param {string} S
 * @return {number}
 */
const numJewelsInStones = (J, S) => {
  const target = [...J]
  const myStone = [...S]
  let count = 0

  myStone.forEach((stone) => {
    target.forEach((sample) => {
      if (stone === sample) {
        count += 1
      }
    })
  })

  return count
}

console.log(numJewelsInStones('aA', 'aAAbbbb'))