QS.js

var QS = (function(loc) {
    var data = {},
        query = loc.search.substring(1),
        vars = query.split('&'),
        dUc = decodeURIComponent;

    vars.forEach(function(couple) {
        var pair = couple.split('='),
            key = dUc(pair[0]),
            value = dUc(pair[1]);

        data[key] = value;
    });

    return {
        get: function(key) {
            if (data.hasOwnProperty(key)) {
                return data[key];
            }
            return null;
        }
    }
}(window.location));

queryString.coffee

    queryString: {
        parse: ->
            params = null
            results = decodeURIComponent(location.search)
                .replace('?', '')
                .split('&')
                .map((qParam) ->
                    [key, value] = qParam.split '='
                    if value?
                        params ?= {}
                        params[key] = value
                )

            return params

        getParameter: (name) ->
            params = @parse()
            return null if not params?
            return params[name]
    }