index.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".

//     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.

// Solution

const numJewelsInStones = (J, S) => {
    let count = 0;

    for (let i = 0; i < S.length; i++) {
        if (J.includes(S[i])) {
            count += 1;
        }
    }
    return count;
};