Javascript function that counts occurrencies of a substring in a string

countOccurrenciesInString.js

/** Function that counts occurrencies of a substring in a string;
 * @param  {String} string               The string
 * @param  {String} subString            The sub string to search for
 * @param  {Boolean} [allowOverlapping]  Optional. (Default:false)
 * @return {Integer}                     Total count of occurrencies
 */
function occurrencesCount(string, subString, allowOverlapping) {
    string += "";
    subString += "";
    if (subString.length <= 0) return (string.length + 1);

    var n = 0,
        pos = 0,
        step = allowOverlapping ? 1 : subString.length;

    while (true) {
        pos = string.indexOf(subString, pos);
        if (pos >= 0) {
            ++n;
            pos += step;
        } else break;
    }
    return n;
}

// Here's a few simple examples
occurrencesCount("foofoofoo", "bar"); // Will return 0
occurrencesCount("foofoofoo", "foo"); // Will return 3
occurrencesCount("foofoofoo", "foofoo"); // Will return 1

// Here's an example with allowOverlapping set to true
occurrencesCount("foofoofoo", "foofoo", true); // Will return 2