countOccurrences
Given a string and a character, count how many times the character appears in the string.
Examples
countOccurrences('hello', 'l') → 2
countOccurrences('programming', 'm') → 2
countOccurrences('banana', 'a') → 3
Starter code
function countOccurrences(str, char) {
}
Complexity of the optimal solution
Time O(n), space O(1). The function loops through the input string once. The execution time scales linearly with the length of the string (n). The space used for the counter is constant.