Count the occurrences of substring in a string.

occurrences.js

/** 
* Count the occurrences of substring in a string;
*
* @method occurrences
* @param haystack {String}
* @param needle {String}
* @param [allowOverlapping=false] {Boolean}
* @author Vitim.us http://stackoverflow.com/questions/4009756/how-to-count-string-occurrence-in-string/7924240#7924240
*/
function occurrences(haystack, needle, allowOverlapping) {

	haystack = haystack + '', needle = needle + '';
	
	if (needle.length <= 0)
	{
		return (haystack.length + 1);
	}

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

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

	return n;
}