A snippet for creating a map with multiple layers in CartoDB

map_snippet.js

// the center point of the map on load. Change this to adjust the center point of the map.
var map_centerpoint = [40.712784, -74.005941];
// zoom level of the map on load. Higher number zooms the map in closer
var zoom_level = 11
// your visualization layer from CartoDB
var myVizLayer = 'https://richard-datapolitan.cartodb.com/api/v2/viz/c35e85b2-5370-11e5-b844-0e9d821ea90d/viz.json';
// the name of the CartoDB table you want to query against
var point_table_name = 'map_data_sgr';
var line_table_name = 'nyct_routes_1';
var sublayers=[];
////////// End of key parameters ///////////////
// create the map object
function init(){
    var map = new L.Map('map', {
        center: map_centerpoint, //center of map
        zoom: zoom_level //zoom level of map
      });
    // initializes the basemap. This uses the basic positron background
    var basemap = L.tileLayer('http://{s}.basemaps.cartocdn.com/light_nolabels/{z}/{x}/{y}.png',{
        attribution: '&copy; <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors, &copy; <a href="http://cartodb.com/attributions">CartoDB</a>'
      }).addTo(map);

    var myLayer = cartodb.createLayer(map, myVizLayer) 
      .addTo(map)
      .done(function(layer) {
         for (var i = 0; i < layer.getSubLayerCount(); i++) {
             sublayers[i] = layer.getSubLayer(i);
          } 
          layer.setInteraction(true);
          layer.on('error', function(err) {
              console.log('error: ' + err);
          });
    });
} //end function init
init();

$(document).ready(function() {
  $(".subway-route").click(function(event) {
      var route = event.target.id;
      var pt_sql,rt_sql;
      if (route == 'reset'){
        pt_sql = "SELECT * FROM " + point_table_name;
        rt_sql = "SELECT * FROM " + line_table_name;
      } else {
        pt_sql = "SELECT * FROM " + point_table_name + " WHERE numbers_letters ILIKE '%" + route + "%'";
        rt_sql = "SELECT * FROM " + line_table_name + " WHERE route_id ILIKE '%" + route + "%'";
      };
      // console.log(pt_sql);
      sublayers[2].setSQL(pt_sql);
      // console.log(rt_sql);
      sublayers[0].setSQL(rt_sql);
      sublayers[1].setSQL(rt_sql);
  });
});