JavaScript + DOM implementation of http://dvcs.w3.org/hg/url/raw-file/tip/Overview.html

URL_polyfill.js

void function() {
    "use strict";
    var global = this;

    //Mini alternative https://gist.github.com/2428561

    //Uses
    //https://gist.github.com/1384398
    //https://gist.github.com/1235332

    function parseSearch(s, match, notMatch, valueOnly, nameOnly) {
        var result = []
            , parts = s.slice(1).split('&')
            , i = 0
            , part
            , key
            , value
        ;

        for( ; i < parts.length; i++ ) {
            part = parts[i];
            key = part.split('=', 1)[0];

            if( key && (match == void 0 || match == key) && (notMatch == void 0 || notMatch != key) ) {
                value = part.slice(key.length + 1);
                result.push(valueOnly ? value : nameOnly ? key : [key, value]);
            }
        }
        return result;
    }

    function serializeParsed(array) {
        var i = 0
            , l = array.length
            , result = []
            , pair
        ;

        for( ; i < l ; ++i ) {
            pair = array[i];
            result[i] = pair[1] !== '' ? pair.join('=') : pair[0];
        }

        return result.join('&');
    }

    function _URL(url, base) {
        if( this === global || this === null ) {
            throw new TypeError("DOM object constructor cannot be called as a function");
    	}

        if( !url )
            throw new TypeError('Invalid argument');

        var thisObj = this
        //https://gist.github.com/1235332
            , m = String(url).replace(/^\s+|\s+$/g, '').match(/^([^:\/?#]+:)?(\/\/(?:[^:@]*(?::[^:@]*)?@)?(([^:\/?#]*)(?::(\d*))?))?([^?#]*)(\?[^#]*)?(#[\s\S]*)?/)
        ;

        thisObj.href = m[0];
        if( thisObj.href === '' ) {
            throw new TypeError('Invalid URL');
        }
        thisObj.protocol = m[1] || "";
        thisObj.authority = m[2] || "";
        thisObj.host = m[3] || "";
        thisObj.hostname = m[4] || "";
        thisObj.port = m[5] || "";
        thisObj.pathname = m[6] || "";
        thisObj.search = m[7] || "";
        thisObj.hash = m[8] || "";

        var match;
        if( (match = thisObj.pathname.match(/\/([^\/]+)$/)) ) {
            thisObj.filename = match[1];
        }
        thisObj.filename = '';

        thisObj.parameterNames = Object.create ? Object.create(null) : {};

        var searchArray = parseSearch(thisObj.search, void 0, void 0, void 0, true)
            , i = 0
            , l = searchArray.length
            , result = []
            , name
        ;
        for( ; i < l ; ++i ) {
            name = searchArray[i];
            if( !(name in thisObj.parameterNames) ) {
                thisObj.parameterNames[name] = true;
                result.push(name);
            }
        }
    }

    _URL.prototype = {
        toString: function() {
            return this.href;
        },

        // NOT IMPLEMENTED
        // get username() {
        //   return this._anchorElement.username;
        // },
        // set username(value) {
        //   this._anchorElement.username = value;
        // },

        // get password() {
        //   return this._anchorElement.password;
        // },
        // set password(value) {
        //   this._anchorElement.password = value;
        // },

        // get origin() {
        //   return this._anchorElement.origin;
        // },


        getParameter: function(name) {
            return this.getParameterAll(name).pop();
        },

        getParameterAll: function(name) {
            return parseSearch(this.search, name + "", void 0, true);
        },

        appendParameter: function(name, values) {
            this.parameterNames[name] = true;

            if( !Array.isArray(values) ) {
                values = [values];
            }

            var parsed = parseSearch(this.search);
            for( var i = 0; i < values.length; i++ ) {
                parsed.push([name, values[i]]);
            }

            parsed = serializeParsed(parsed);

            this.search = parsed ? ("?" + parsed) : "";
            _recalculateHref.call(this);
        },

        clearParameter: function(name) {
            if( name in this.parameterNames ) {
                delete this.parameterNames[name];
            }

            name = serializeParsed(
                parseSearch(this.search, void 0, name)
            );

            this.search = name ? ("?" + name) : "";
            _recalculateHref.call(this);
        }
    };

    function _recalculateHref() {
        this.href = this.protocol + "//" + this.host + this.pathname + this.search;
    }

    var oldURL;

    if( oldURL = global.URL || global.webkitURL || global.mozURL ) {
        if( oldURL.createObjectURL ) {
            _URL.createObjectURL = function(blob) {
                return this.createObjectURL.apply(this, arguments);
            }.bind(oldURL);
        }

        if( oldURL.revokeObjectURL ) {
            _URL.revokeObjectURL = function(url) {
                return this.revokeObjectURL.apply(this, arguments);
            }.bind(oldURL);
        }
    }

    oldURL = null;
    /*
     // Methods should not be enumerable.
     Object.defineProperty(_URL.prototype, 'toString', {enumerable: false});
     Object.defineProperty(_URL.prototype, 'getParameter', {enumerable: false});
     Object.defineProperty(_URL.prototype, 'getParameterAll', {enumerable: false});
     Object.defineProperty(_URL.prototype, 'appendParameter', {enumerable: false});
     Object.defineProperty(_URL.prototype, 'clearParameter', {enumerable: false});
     Object.defineProperty(_URL, 'createObjectURL', {enumerable: false});
     Object.defineProperty(_URL, 'revokeObjectURL', {enumerable: false});*/


    //EXPORT
    global["URL"] = _URL;

}.call(window);