[LeetCode] 771. Jewels and Stones (javascript)

 

/**
 * @param {string} J
 * @param {string} S
 * @return {number}
 */
var numJewelsInStones = function(J, S) {
    const cnt={};
    for(let i=0;i<S.length;i+=1){
        if(!cnt[S[i]]){
            cnt[S[i]]=1;
        }else{
            cnt[S[i]]+=1;
        }
    }
  
    let sum=0;
    for(let i=0;i<J.length;i+=1){
        if(cnt[J[i]]){
            sum+=cnt[J[i]];
        }
    }
    return sum;
};