JewelsAndStones.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.
*/

/**
 * @param {string} J
 * @param {string} S
 * @return {number}
 */
var numJewelsInStones = function(J, S) {
    let count = 0;
    
    for(let char of S) {
        if(J.indexOf(char) > -1) {
            count++;
        }
    }
    
    return count;
    
};