Laravel's pluralization logic in JavaScript

String.pluralization.js

// replace occurences of :vars in the string.
// "This :thing is great!".format
String.prototype.format = function(replacements) {
	var str = this;
	for (var key in replacements) {
		if (replacements.hasOwnProperty(key)) {
			str = str.replace(':' + key, replacements[key]);
		}
	}
	return str;
};

// Adds the ability to pluralize strings using Laravel's pluralization engine
// "{0} No files selected|{1} 1 file selected|[2,Inf] :count files selected".pluralize(4, { count : 4 })
String.prototype.pluralize = function(number, replacements) {

	var terms = this.split('|');
	var regex = /^\s*({[0-9]+}|\[[0-9]+,Inf])\s*(.*)$/g;
	var matches;

	for (var i in terms) {

		if (!terms.hasOwnProperty(i)) {
			continue;
		}

		var term = terms[i];

		while ((matches = regex.exec(term)) !== null) {
			// This is necessary to avoid infinite loops with zero-width matches
			if (matches.index === regex.lastIndex) {
				regex.lastIndex++;
			}

			var isTheOne = false;
			var str = '';

			for (var groupIndex in matches) {

				if (!matches.hasOwnProperty(groupIndex)) {
					continue;
				}

				if (groupIndex === "2" && isTheOne) {
					str = matches[groupIndex];
				}

				if (groupIndex !== "1") {
					continue;
				}

				var match = matches[groupIndex].substring(1, matches[groupIndex].length - 1).toLowerCase();

				if (match.indexOf(',') >= 0) {
					var between = match.split(',');
					var start = between[0] === '-inf' ? Number.MIN_VALUE : between[0];
					var end = between[1] === 'inf' ? Number.MAX_VALUE : between[1];

					if (number >= start && number <= end) {
						isTheOne = true;
					}
				} else if (parseInt(match) === number) {
					isTheOne = true;
				}

			}

			if (isTheOne) {
				return str.get(replacements);
			}
		}
	}

	return this;

};