387. First Unique Character in a String - 《leetcode》

Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1.

Examples:

s = "leetcode"
return 0.
s = "loveleetcode",
return 2.

Note: You may assume the string contain only lowercase letters.

/**
 * @param {string} s
 * @return {number}
 */
var firstUniqChar = function(s) {
    const count = new Array(26);
    for (let i = 0; i < count.length; i++) {
        count[i] = 0;
    }
    for (let i = 0; i < s.length; i++) {
        count[s.charCodeAt(i) - 97]++;
    }
    for (let i = 0; i < s.length; i++) {
        if (count[s.charCodeAt(i) - 97] === 1) {
            return i;
        }
    }
    return -1;
};