A class to parse and resolve URLs

URLParser.js

var URLParser = (function () {

	// Return class
	var URLParser = function (url_str) {
		this.hash = "";
		this.host = null;
		this.hostname = null;
		this.pathname = "";
		this.protocol = null;
		this.search = "";
		this.slashes = false;
		this.auth = null;
		this.port = null;

		if (typeof(url_str) === "string") {
			this.parse(url_str);
		}
	};



	// Regex
	var re_protocol = /^[a-z][a-z0-9\+\-\.]*:/i,
		re_double_slash = /^\/{2}/,
		re_auth = /^(.*)@/i,
		re_port = /:(\d*)$/i,
		re_hierarchy_sep = /([\/\?\#]|$)/,
		re_path_sep = /([\?\#]|$)/,
		re_search_sep = /([\#]|$)/;



	// Path operations
	var normalize_path = function (path) {
		return path;
	};
	var join_paths = function (base, ext) {
		if (ext[0] === "/") {
			// Absolute
			return ext;
		}

		// Joined
		var p = base.lastIndexOf("/");
		if (p < 0) {
			// Absolute
			return ext;
		}

		// Join
		return base.substr(0, p + 1) + ext;
	};



	// Functions
	URLParser.prototype = {
		constructor: URLParser,

		parse: function (url_str, ignore_double_slash) {
			// Setup object
			var m, url_part;

			// Protocol
			if ((m = re_protocol.exec(url_str)) !== null) {
				this.protocol = m[0].toLowerCase();
				url_str = url_str.substr(m[0].length);
			}
			else {
				this.protocol = null;
			}

			// Slashes
			if (!ignore_double_slash && (m = re_double_slash.exec(url_str)) !== null) {
				// Process auth and host
				this.slashes = true;
				url_str = url_str.substr(m[0].length);

				// Find end
				m = re_hierarchy_sep.exec(url_str);
				url_part = url_str.substr(0, m.index);
				url_str = url_str.substr(m.index);

				// Auth
				if ((m = re_auth.exec(url_part)) !== null) {
					this.auth = m[1];
					url_part = url_part.substr(m[0].length);
				}
				else {
					this.auth = null;
				}

				// Port
				if ((m = re_port.exec(url_part)) !== null) {
					this.port = parseInt(m[1], 10);
					url_part = url_part.substr(0, m.index);
				}
				else {
					this.port = null;
				}

				// Host name
				url_part = url_part.toLowerCase();
				this.hostname = url_part;
				this.host = url_part;
				if (this.port !== null) {
					this.host += ":";
					this.host += this.port;
				}
			}
			else {
				// Null
				this.slashes = false;
				this.host = null;
				this.hostname = null;
				this.auth = null;
				this.port = null;
			}

			// Path
			m = re_path_sep.exec(url_str);
			this.pathname = url_str.substr(0, m.index);
			if (this.pathname.length === 0 && this.slashes) {
				this.pathname = "/";
			}
			url_str = url_str.substr(m.index);

			// Search
			m = re_search_sep.exec(url_str);
			this.search = url_str.substr(0, m.index);
			url_str = url_str.substr(m.index);

			// Fragment
			this.hash = url_str;

			// Done
			return this;
		},
		resolve: function (to) {
			// Other parser
			var other = new URLParser(to);

			// Protocol
			if (other.protocol === null) {
				// Copy protocol
				other.protocol = this.protocol;
			}

			// Hierarchy
			if (!other.slashes && this.slashes) {
				// Copy host
				other.slashes = true;
				other.host = this.host;
				other.hostname = this.hostname;
				other.auth = this.auth;
				other.port = this.port;
			}

			// Path
			if (other.pathname.length > 0) {
				// Join paths
				other.pathname = normalize_path(join_paths(this.pathname, other.pathname));
			}
			else {
				// Copy path
				other.pathname = this.pathname;

				// Search
				if (other.search.length === 0) {
					// Copy search
					other.search = this.search;

					// Hash
					if (other.hash.length === 0) {
						// Copy hash
						other.hash = this.hash;
					}
				}
			}

			// Done
			return other.join();
		},
		join: function () {
			// Form
			var url_str = "";

			if (this.protocol !== null) {
				url_str += this.protocol;
			}

			if (this.slashes) {
				url_str += "//";

				if (this.auth !== null) {
					url_str += this.auth;
					url_str += "@";
				}

				url_str += this.hostname;

				if (this.port !== null) {
					url_str += ":";
					url_str += this.port;
				}
			}

			url_str += this.pathname;
			url_str += this.search;
			url_str += this.hash;

			return url_str;
		},
	};



	// Functions
	return URLParser;

})();