Add custom properties to leaflet/mapbox geoJSON marker - leaflet

Question

The two functions of relevance are below.
I want to add custom properties to the markers. To be specific, the userID to the properties object. It doesn't have to be there but what i've done below does not work.
Is there no way to pass custom properties?
initMap:function(){
L.mapbox.accessToken = 'myToken';
Shop.el.map = L.mapbox.map('map');
Shop.el.retailersLayer = L.mapbox.featureLayer().addTo(Shop.el.map);
Shop.el.retailMarkers = [];
// add tile layer
L.tileLayer('myLayerKey', {
maxZoom: 18
}).addTo(Shop.el.map);
// By default, center map over Colorado
Shop.el.map.setView([39.7392, -104.9847], 12);
},
addGeoJSONToMap:function(retailers){
// format geoJSON
jQuery.each(retailers, function(index, val) {
// Push each on of the retail locations into the retailMarkers array
Shop.el.retailMarkers.push(
{
type: 'Feature',
geometry: {
type: 'Point',
coordinates: [parseFloat(val.lng), parseFloat(val.lat)]
},
properties: {
'userId':'99', <------------------------ This does not work.
'marker-color': '#193441',
'marker-symbol': 'star-stroked',
title: ' val.name,
description: 'Marker Description'
},
}
);
});
// Add the retail location as markers to the map
Shop.el.retailersLayer.setGeoJSON({
type: 'FeatureCollection',
features: Shop.el.retailMarkers
});
},

Answer 1

Never mind. This DOES work. The property is then found in:
marker.features.userID