LeetCode 771 宝石和石头

Input: J = "aA", S = "aAAbbbb"
Output: 3

解：J为宝石字符串，S为包含宝石的字符串，J中的字母如果在S中出现数字就➕1

var numJewelsInStones = function(J, S) {
    let array1 = J.split('');
    let array2 = S.split('');
    let count = 0;
    let obj = {};
    array1.forEach(item=>{
        obj[item] = 1;
    })
    array2.forEach(item=>{
        if(obj[item]){
            count++;
        }
    })
    return count;
};