css Audio - Active file-generic CSS - Active Generic - Active HTML - Active JS - Active SVG - Active Text - Active file-generic Video - Active header Love html icon-new-collection icon-person icon-team numbered-list123 pop-out spinner split-screen star tv

Pen Settings

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource

You're using npm packages, so we've auto-selected Babel for you here, which we require to process imports and make it all work. If you need to use a different JavaScript preprocessor, remove the packages in the npm tab.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Use npm Packages

We can make npm packages available for you to use in your JavaScript. We use webpack to prepare them and make them available to import. We'll also process your JavaScript with Babel.

⚠️ This feature can only be used by logged in users.

Code Indentation


Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

              <div id="header">
   <span class="title">
     Population Density of California Counties
   <select name="Classification Type" id="type">
     <option value="quantile">Quantile Classification</option>
     <option value="jenks">Jenks Classification</option>

<div id="map"></div>

<div id="legend">
   <strong>Population Density</strong>
   <span class="type">Quantile Classification</span>
   <div class="breaks">
body {
   height: 100%;
   font-family: Helvetica;

body {
   margin: 0;
   padding: 0;

#map {
   height: 100%;
   width: 100%;
   position: relative

#header {
   background: #333;
   padding: 1vw;
   padding-left: 2vw;
   height: 3vw;

#header .title {
   color: #EEE;
   font-size: 1.6vw;
   line-height: 3.4vw;

#type {
   background: #222;
   border: solid 1px #888;
   color: #EEE;
   font-size: 1.2vw;
   float: right

#legend {
   background: #FFFFFF;
   position: absolute;
   width: 18vw;
   height: auto;
   bottom: 1vw;
   right: 1vw;
   padding: 12px;

#legend .icon {
   width: 1.5vw;
   height: 1.5vw;
   margin-right: 2vw;
   float: left;

#legend .sub {
   font-size: .9vw;
   color: #444;

#legend .type {
   font-size: 1vw;
   color: #666;
              // Public auth for initializing the map
var mapMain = 'stevepepple.lkojhhoh';
L.mapbox.accessToken = 'pk.eyJ1Ijoic3RldmVwZXBwbGUiLCJhIjoiTmd4T0wyNCJ9.1-jWg2J5XmFfnBAhyrORmw';

// Quantile or Jenks classification
var type = $("#type").val();
var breaks;

// Color scale using chroma.js
var scale = chroma.scale('YlOrBr');

// Create the base map using Mapbox
map = L.mapbox.map('map', mapMain, {
   attributionControl: false,
   maxZoom: 12,
   minZoom: 5
}).setView([34.0261899, -118.2455643], 8);

// Calculate population density for each county
_.each(counties.features, function(feature) {
   // Population from 2010 Census
   var pop = feature.properties.POP;
   // Calcualate desnity as popluation / square meters 
   var area = turf.area(feature.geometry);
   var sq_miles = area * 0.000000386102158542;
   feature.properties.pop_density = (pop / sq_miles);


// Show the Choropleth of Population Density
function updateMap() {
   // Make a Turf collection for analysis
   collection = turf.featurecollection(counties.features);

   // Basic UI for select Jenks or Quantile classification
   if (type == "jenks") {
      breaks = turf.jenks(collection, "pop_density", 8);
   } else {
      breaks = turf.quantile(collection, "pop_density", [25, 50, 75, 99]);
   // Get the color when adding to the map
   var layer = L.geoJson(counties, {
      style: getStyle
   // Fit to map to counties and set the legend

   function getStyle(feature) {
      var pop = feature.properties.POP;
      var pop_density = feature.properties.pop_density;
      return {
         fillColor: getColor(pop_density),
         fillOpacity: 0.7,
         weight: 1,
         opacity: 0.2,
         color: 'black'

   function updateLegend() {
      for (var i = 0; i < breaks.length; i++) {
         var density = Math.round(breaks[i] * 100) / 100;
         var background = scale(i / (breaks.length));
         $(".breaks").append("<p><div class='icon' style='background: " + background + "'></div><span> " + density + " <span class='sub'>pop / mi<sup>2</sup></span></span></p>");

/* Get color depending on population density value */
function getColor(d) {
   // Select a color scale from Color Brewer 
   var color = scale(0);
   // Place the feature based upon breaks
   for (var i = breaks.length - 1; i >= 0; i--) {
      if (d < breaks[i]) {
         // Automatic way to select the color by class
         var percentage = (i / (breaks.length));
         color = scale(percentage);
   return color;
🕑 One or more of the npm packages you are using needs to be built. You're the first person to ever need it! We're building it right now and your preview will start updating again when it's ready.
Loading ..................