Immediately-Invoked Function Expression (IIFE) for generating & validating IPv4 IP addresses

ip.js

var ip = (function() {
	var _privateIps = [
	  '10.0.0.0',
	  '10.255.255.255',
	  '172.16.0.0',
	  '172.31.255.255',
	  '192.168.0.0',
	  '192.168.255.255'
	];

	var _publicIps = [
	  '0.0.0.0',
	  '255.255.255.255',
	];

	// PRIVATE FUNCTIONS
	this._generateInRange = function(min, max) {
		return Math.floor(Math.random() * (max - min + 1)) + min;
	}

	this._generateOctets = function() {
		return [_generateInRange(0,255), _generateInRange(0,255), _generateInRange(0,255),_generateInRange(0,255)];
	}

	this._concatenateOctets = function(octets) {
		var ip = '';
		for (var i = 0; i < octets.length; i++) {
			ip += octets[i];
			ip += (i < octets.length - 1) ? '.' : '';
		}
		return ip;
	}

	// PUBLIC FUNCTIONS
	this.isPrivate = function(ip) {
	  return /^10\.|^192\.168\.|^172\.16\.|^172\.17\.|^172\.18\.|^172\.19\.|^172\.20\.|^172\.21\.|^172\.22\.|^172\.23\.|^172\.24\.|^172\.25\.|^172\.26\.|^172\.27\.|^172\.28\.|^172\.29\.|^172\.30\.|^172\.31\./.test(ip);
	}

	this.isPublic = function(ip) {
		return !isPrivate(ip);
	}

	this.private = function() {
		var ip = '';
		var networks = [10, 172, 192];
		var octets = [networks[_generateInRange(0,2)]];

		// generate address
		switch(octets[0]) {
			case 10:
				octets.push(_generateInRange(0, 255), _generateInRange(0, 255), _generateInRange(0, 255))
				break;
			case 172:
				octets.push(_generateInRange(16, 31), _generateInRange(0, 255), _generateInRange(0, 255))
				break;
			case 192:
				octets.push(168, _generateInRange(0, 255), _generateInRange(0, 255));
				break;
			default:
				return ip;
		}

		return _concatenateOctets(octets);
	};

	this.public = function() {
		var ip = '';
		octets = _generateOctets();
		var privateNetworks = [10, 172, 192];

		// regenerate if private network octets were generated
		while (octets.indexOf(privateNetworks) >= 0) {
			switch(octets[0]) {
				case 10:
					octets = _generateOctets();
					break;
				case 172:
					if (octets[1] >= 16 || octete[1] <= 31) {
						octets = _generateOctets();
					}
					break;
				case 192:
					if (octets[1] === 168) {
						octets = _generateOctets();
					}
					break;
				default:
					break;
			}
		}

		return _concatenateOctets(octets);
	}

	return {
		private: private,
		public: public,
		isPrivate: isPrivate,
		isPublic: isPublic
	}
})();