Adding GeoJSON data to a Leaflet map (with a timer) - 1.0 beta version

by Alex Azuero

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet/v1.0.0-beta.2/leaflet.css">
<script src="http://cdn.leafletjs.com/leaflet/v1.0.0-beta.2/leaflet.js"></script>
<div id="map"></div>

CSS

html, body, #map {
    height: 100%;
    width:100%;
    padding:0px;
    margin:0px;
    background: white;
}
.info {
    padding: 6px 8px;
    font: 14px/16px Arial, Helvetica, sans-serif;
    background: white;
    background: rgba(255, 255, 255, 0.8);
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.2);
    border-radius: 5px;
}
.info h4 {
    margin: 0 0 5px;
    color: #777;
}
.legend {
    text-align: left;
    line-height: 18px;
    color: #555;
}
.legend i {
    width: 18px;
    height: 18px;
    float: left;
    margin-right: 8px;
    opacity: 0.7;
}
.legend .colorcircle {
    border-radius: 50%;
    width: 15px;
    height: 15px;
    margin-top: 0px;
}
.legend .circlepadding {
    border-radius: 50%;
    margin-top: 0px;
    background: rgba(255, 255, 255, 0.8);
}

JavaScript

/////////////////////////////////////////////////////////////////////////////////////////////
//setting up the map//
/////////////////////////////////////////////////////////////////////////////////////////////

// set center coordinates
var centerlat = 34.05;
var centerlon = -118.25;

// set default zoom level
var zoomLevel = 10;

// initialize map
var map = L.map('map').setView([centerlat, centerlon], zoomLevel);

// set source for map tiles
ATTR = '&copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, ' +
'<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a> | ' +
'&copy; <a href="http://cartodb.com/attributions">CartoDB</a>';

CDB_URL = 'http://{s}.basemaps.cartocdn.com/light_all/{z}/{x}/{y}.png';

// add tiles to map
L.tileLayer(CDB_URL, {attribution: ATTR}).addTo(map);

/////////////////////////////////////////////////////////////////////////////////////////////
//displaying the data//
/////////////////////////////////////////////////////////////////////////////////////////////

//create an empty GeoJSON layer
var dotLayer = L.geoJson(false, {
    pointToLayer: function (feature, latlng) {
        return L.circleMarker(latlng, style(feature));
    },
    onEachFeature: onEachDot
}).addTo(map);

//add dots every [dotInterval] ms until there are [dotCount] of them
var dotIndex = 1;
var dotCount = 5000;
var dotInterval = 50;
var dotClock = setInterval(dotDot, dotInterval);

function dotDot() {
    if (dotIndex == dotCount) clearInterval(dotClock);

    //create a new dot and add it to the existing layer
    var newDot = make_dot(dotIndex);
    dotLayer.addData(newDot);

    ++dotIndex;
}

/////////////////////////////////////////////////////////////////////////////////////////////
//styling functions//
/////////////////////////////////////////////////////////////////////////////////////////////

//create color ramp
function getColor(y) {
    return y > 2000 ? '#6068F0' : y > 1980 ? '#7660C9' : y > 1960 ? '#8C58A3' : y >...