Recursively count the number of characters

by Hari Menon

JavaScript

function numOccurs(char, str) {
    var sum = 0;
    if (!str) {
        return sum;
    }
    if (char.test(str.charAt(0))) {
        sum += 1;
    }
    return sum + numOccurs(char, str.substring(1));
}

//console.log(numOccurs(/[a-z]/, 'abracadabra'));
console.log(numOccurs(/a/, 'abracadabra'));