mbHelper addSourceAndLayers() example

mbhelper-example.js

mbHelper.addSourceAndLayers.call(map,
    { // source
        "type": "vector",
        "url": "mapbox://mapbox.us_census_states_2015",
        "name": "states"
    }, [ // layers
        { // layer one
            "id": "states-join",
            "type": "fill",
            "source-layer": 'states',
            "paint": {
              "fill-color": 'transparent'
            },
            "beforeLayer": "water" // <== this is different from mapbox native specs
        },
        { // layer two
            "id": "states-join-hover",
            "type": "line",
            "source-layer": 'states',
            "paint": {
                "line-color": '#4D90FE',
                "line-width": 4,
                "line-blur": 2
            },
            "filter": ["==", "name", ""]
        }
    ]).then(() => {
        // do some stuff
        });