Creating a map

In OpenLayers, a map is a collection of layers that get rendered to a web page. To create a map, you need some markup (HTML) that creates the map viewport (e.g. a <div> element), a bit of style to give the map viewport the appropriate dimensions on your page, and map initialization code.

Working example

Make sure you've completed the setup instructions to install dependencies and get the development server running.

Now let's create a fully working example of an OpenLayers map. At a minimum, we need some markup with a container element for a map, and an OpenLayers Map instance which we configure with a layer and a view.

The markup

First, we create an index.html file in the root of the workshop directory:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>OpenLayers</title>
    <style>
      html, body, #map-container {
        margin: 0;
        height: 100%;
        width: 100%;
        font-family: sans-serif;
      }
    </style>
  </head>
  <body>
    <div id="map-container"></div>
  </body>
</html>

Note that we do not need to include any <script> for our application. Our webpack setup takes care of that. Our <style> makes the map container fill the whole page, and we will use the container <div> with the map-container id as target for the map.

The application

To work with OpenLayers, we import the ol package from npm. This is done with an npm install in our terminal:

npm install --save ol

Next, as entry point of the application, we create a main.js file, and also save it in the root of the workshop directory:

import 'ol/ol.css';
import Map from 'ol/map';
import View from 'ol/view';
import TileLayer from 'ol/layer/tile';
import XYZSource from 'ol/source/xyz';

new Map({
  target: 'map-container',
  layers: [
    new TileLayer({
      source: new XYZSource({
        url: 'http://tile.stamen.com/terrain/{z}/{x}/{y}.jpg'
      })
    })
  ],
  view: new View({
    center: [0, 0],
    zoom: 2
  })
});

At the top, we import the required modules from the ol package. Note the 'ol/ol.css' import, which adds the styles that OpenLayers requires for its basic UI components. With everything we need imported, we create move on and create a Map. The target points to the container <div> we have in our markup. We configure the map with a tiled image layer (TileLayer) and an XYZSource. Finally, the View defines the initial center and zoom.

Viewing the map

Now our application is ready for testing. Let's open the working map in a web browser: http://localhost:3000/. This is how it should look:

A map of the world
A map of the world

In the final chapter of the workshop, we will learn how create a production build of the application for deployment.

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