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.

              <svg viewBox="0 0 960 600">
  <!--  we'll put SVG <path> elements here with D3js -->

  Blog post:
  <a href="" target="_blank">
    "Get Started Creating D3 Maps"

  Canvas version:
  <a href="" target="_blank">

<script src=""></script>
<script src=""></script>
              body {
  margin: 5px;
  text-align: center;
  background-color: #007da4;

svg {
  width: calc(100vmin - 10px);
  outline: 1px solid white;
  stroke-linejoin: round;
  stroke-linecap: round;

path.feature {
  stroke-width: 1px;
  stroke: white;
  fill: none;

p, a {
  color: white;
  font-family: sans-serif;
  font-size: 0.8rem;

              // make D3 aware of the <svg> element in the HTML
var svg ="svg");

// get <svg> width and height from HTML instead of hard-coding values
var svgWidth = +svg.attr("viewBox").split(" ")[2],
  svgHeight = +svg.attr("viewBox").split(" ")[3];

// define the map projection
// we're going from spherical latitude/longitude coordinates to a flat map
var projection = d3
  // use Mercator for now, sigh, because of web map ubiquity...
  // shift the projection translation offset to half of the parent <svg> width and height
  .translate([svgWidth / 2, svgHeight / 2])
  // [0, 0] is redundant, but you could change the initial center [longitude, latitude]
  .center([0, 0])
  // [0, 0, 0] is also redundant, but you can change the rotation along 3 axes
  // this property is really fun, so experiment with different values!
  .rotate([0, 0, 0])
  // set an initial scale value
  .scale(svgWidth / (2 * Math.PI));

// NOTE: if you want to skip setting the translate and scale values
// and instead zoom out to the whole world, you can just use this shortcut:
// projection.fitSize([svgWidth, svgHeight], {
//   type: "Sphere"
// });

// "d3.geoPath" helps convert from geojson coordinates to <svg> or <canvas> drawing instructions
// it needs to know about the projection that was defined above

// I like to refer to it as a "geographic path generator" throughout the code
var geoPathGenerator = d3.geoPath().projection(projection);

// request publicly available and hosted world topojson data,
// convert it to geojson,
// and then draw it in the <svg>
  .then(function(loadedTopoJson) {
    // use the concept of a topojson "mesh" to convert topojson
    // to a single, efficient geojson geometry
    var geoJson = topojson.mesh(

    // and then draw the single geojson representing all country polygons
    // as a single <path> element within the <svg> parent element
    // (1 geojson geometry results in only 1 <path> element)
      .attr("d", geoPathGenerator(geoJson))
      .attr("class", "feature");

    // an alternate and very common approach is to convert the topojson to a geojson feature collection,
    // where each country polygon is represented by an individual geojson feature
    // and thus each geojson feature is drawn as a unique <path> element within the <svg> parent element    
    // RESULT:
    // many geojson features resulting in as many <path> elements

    // WHY?
    // this is useful for thematic mapping

    // HOW?
    // you can uncomment the code below and try it out

    // var geoJson = topojson.feature(loadedTopoJson,;

    // svg
    //   .selectAll("path")
    //   .data(geoJson.features)
    //   .enter()
    //   .append("path")
    //   .attr("d", geoPathGenerator)
    //   .attr("class", "feature");

🕑 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.