/**
 * @param {string} s
 * @return {number}
 */
var firstUniqChar = function(s) {
    let count = {}
    let ans = -1;
    for (let letter of s) {
        if (!count[letter]) {
            count[letter] = 0;
        }
        count[letter]++;
    }
    
    for (let key in count) {
        if (count[key] === 1) {
            ans = s.indexOf(key);
            break;
        }
    }
    return ans;
};