Creating GeoJson

map.js

function drawIndexReportMap(){
  L.mapbox.accessToken = "YOUR_TOKEN";

  var map = L.mapbox.map("map", "lizvdk.knp8dn4m", { zoomControl: false }):
  
  var featureLayer = L.mapbox.featureLayer().addTo(map);

  featureLayer.on('layeradd', function (e) {
    featureLayer.eachLayer(function(layer) {
      var marker = e.layer,
      feature = marker.feature;
      marker.setIcon(L.divIcon(feature.properties.icon));
    });
  });

  featureLayer.loadURL('/reports.json');

  map.featureLayer.on('ready', function(e) {
    featureLayer.eachLayer(function(layer) {
      item.onclick = function() {
        map.setView(layer.getLatLng(), 19);
        layer.openPopup();
      };
      var content =
                    '<a target="_blank" class="popup" href="' +
                      layer.feature.properties.url + '">' +
                      '<img class="th radius" src="' +
                        layer.feature.properties.photo +
                      '" />' +
                      layer.feature.properties.category +
                      '</a>';
      layer.bindPopup(content, { minWidth: 300 });
    });
  });
}

report.rb

class Report < ActiveRecord::Base
  def self.geojson
    geojson = Hash.new
    features = []
    geojson[:type] = "FeatureCollection"
    geojson[:features] = features
    by_recency.each do |report|
      features << {
        type: "Feature",
        geometry: {
          type: "Point",
          coordinates: [report.longitude, report.latitude]
        },
        properties: {
          category: report.category.name,
          url: "/reports/#{report.id}",
          photo: report.photo.url,
          updated_at: report.display_date,
          id: "report-#{report.id}",
          icon: {
            html: report.category.icon,
            iconSize: [50, 50],
            iconAnchor: [25, 25],
            popupAnchor: [0, -25],
            className: "#{report.marker_color} map-icon"
          }
        }
      }
    end
    geojson
  end
end

reports_controller.rb

class ReportsController < ApplicationController
  def index
    @reports = Report.by_recency
    @geojson = Report.geojson

    respond_to do |format|
     format.html
     format.json { render json: @geojson }
    end
  end
end

Hello Liz;
If you wanted to update that data to the map say using ajax how would you do it,especially the url part where it would be fetching the data to display to the map;eg

$.ajax({
   type: 'json',
   url: 'what url would you put here?',
 ...
});

I have a project i am working on using maps and i am kinda stuck,its on a private repository on bitbucket but i can pull the bit of code for you to help.Thanks in advance,most appreciated.