Check if All A's Appears Before All B's - LeetCode javascript solutions

Problem

Given a string s consisting of only the characters 'a' and 'b', return true **if *every* **'a' *appears before every 'b' in the string*. Otherwise, return false.

Example 1:

Input: s = "aaabbb"
Output: true
Explanation:
The 'a's are at indices 0, 1, and 2, while the 'b's are at indices 3, 4, and 5.
Hence, every 'a' appears before every 'b' and we return true.

Example 2:

Input: s = "abab"
Output: false
Explanation:
There is an 'a' at index 2 and a 'b' at index 1.
Hence, not every 'a' appears before every 'b' and we return false.

Example 3:

Input: s = "bbb"
Output: true
Explanation:
There are no 'a's, hence, every 'a' appears before every 'b' and we return true.

Constraints:

1 <= s.length <= 100
s[i] is either 'a' or 'b'.

Solution

/**
 * @param {string} s
 * @return {boolean}
 */
var checkString = function(s) {
    var hasB = false;
    for (var i = 0; i < s.length; i++) {
        if (s[i] === 'a' && hasB) return false;
        hasB = s[i] === 'b';
    }
    return true;
};

Explain:

nope.

Complexity:

Time complexity : O(n).
Space complexity : O(1).