https://leetcode.com/problems/bulls-and-cows/

bullsAndCows.js

/**
 * @param {string} secret
 * @param {string} guess
 * @return {string}
 */
var getHint = function(secret, guess) {
    let [bulls, cows]  = [0, 0];
    
    const secretDigits = new Array(10).fill(0);
    for(let i=0; i<secret.length; i++){
        secretDigits[secret[i]]++;
    }
    
    for(let i=0; i<guess.length; i++){
        if(secret[i] === guess[i]){
            bulls++;
            secretDigits[secret[i]]--;
        }
    }
    
    for(let i=0; i<guess.length; i++){
        if(secret[i] !== guess[i] && secretDigits[guess[i]]){
            cows++;
            secretDigits[guess[i]]--;
        }
    }
    
    return `${bulls}A${cows}B`;
};