ThreeHammers3_rx-solution

var Rx = require('rx');

var
observablePerPair = function(string) {
    return Rx.Observable.from(string.split('&'));
},
splitEqual = function(pairString) {
    return pairString.split('=');
},
key = function (pair) {
    return pair[0];
},
value = function (pair) {
    return pair[1];
},
objectFromKey = function(key) {
    var obj = {};
    obj[key] = null;
    return obj;
},
scanArray = function(array, value) {
    array.push(value);
    return array;
},
extractValueFromSingleArray = function(a) {
    return (a.length === 1) ? a[0] : a;
},
getOnlyKey = function(obj) {
    keys = Object.keys(obj);
    console.assert(keys.length === 1, 'Too many Keys');
    return keys[0];
},
scanObject = function(obj, value){
    obj[getOnlyKey(obj)] = value;
    return obj;
},
objectizeUrlSearch = function(urlString) {
    var result={};
    Rx.Observable.just(urlString)
        .flatMap(observablePerPair)
        .map(splitEqual)
        .groupBy(key, value)
        .subscribe(function(obs) { Rx.Observable.just(objectFromKey(obs.key)).merge(
                obs
                    .scan(scanArray, [])
                    .map(extractValueFromSingleArray)
            )
                .scan(scanObject)
                .subscribe(
                    function(keyObject) {
                        result = Object.assign(result, keyObject);
                    }
                );
        });
        return result;
    };