Problem

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.

Post analysis

Converting to array and operating on them was unnecessary. Simply could have iterated over string. Probably I had mentally made the problem complex.

Other Simple Solution

var numJewelsInStones = function(J, S) {
    var length = S.length;
    var total = 0;
    for(var i = 0;i<length;i++){
        if(J.indexOf(S[i]) !== -1){
            total++;
        }
    }
    return total
};