Show polygon data from GeoJSON on the map

In this tutorial, we will demonstrate the process of incorporating a GeoJSON polygon overlay onto the map. Through the following steps, you will learn how to seamlessly integrate this feature into your web mapping applications.

NPM module setup

Install the npm package.
```
 npm install --save @maptiler/sdk
```

Include the CSS file.

If you have a bundler that can handle CSS, you can import the CSS


 import "@maptiler/sdk/dist/maptiler-sdk.css";

or include it with a <link /> in the head of the document via the CDN


 <link href='https://cdn.maptiler.com/maptiler-sdk-js/v4.1.0/maptiler-sdk.css' rel='stylesheet' />

Include the following code in your JavaScript file (Example: app.js).


 import * as maptilersdk from '@maptiler/sdk';

 maptilersdk.config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';
 const map = new maptilersdk.Map({
   container: 'map', // container's id or the HTML element to render the map
   style: maptilersdk.MapStyle.STREETS,
      
   center: [-43.206091, -22.920387], // starting position [lng, lat]
   zoom: 11, // starting zoom
      
 });

Replace YOUR_MAPTILER_API_KEY_HERE with your own API key. Make sure to secure the key before you publish it.
The next is up to you. You can center your map wherever you desire (modifying the starting position) and set an appropriate zoom level (modifying the starting zoom) to match your users’ needs. Additionally, you can change the map’s look (by updating the source URL); choose from a range of visually appealing map styles from our extensive MapTiler standard maps, or create your own to truly differentiate your application.
Add event handler for map load event. You will add code to create a GeoJSON source and a vector layer in this handler.
```
 map.on('load', async function() {
    
 });
```
Create GeoJSON source. The following snippet creates GeoJSON source hosted on MapTiler (check out the How to Upload GeoJSON to MapTiler tutorial). Publish the dataset and copy the link to the GeoJSON. Download the Rio de Janeiro sample data.
```
 map.on('load', async function() {
     const geojson = await maptilersdk.data.get('YOUR_MAPTILER_DATASET_ID_HERE');
     map.addSource('rio_cats', {
         type: 'geojson',
         data: geojson
     });
 });
```

Add the vector layer


 map.addLayer({
     'id': 'rio_cats',
     'type': 'fill',
     'source': 'rio_cats',
     'layout': {},
     'paint': {
         'fill-color': '#98b',
         'fill-opacity': 0.8
     }
 });

Basic JavaScript setup

Copy the following code, paste it into your favorite text editor, and save it as a .html file.


 <!DOCTYPE html>
 <html lang="en">
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Display a GeoJSON polygon layer</title>
   <script src="https://cdn.maptiler.com/maptiler-sdk-js/v4.1.0/maptiler-sdk.umd.min.js"></script>
   <link href="https://cdn.maptiler.com/maptiler-sdk-js/v4.1.0/maptiler-sdk.css" rel="stylesheet" />
   <style>
     body { margin: 0; padding: 0; }
     #map { position: absolute; top: 0; bottom: 0; width: 100%; }
   </style>
 </head>
 <body>
   <div id="map"></div>
   <script>
       maptilersdk.config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';      
       const map = new maptilersdk.Map({
         container: 'map', // container's id or the HTML element to render the map
         style: maptilersdk.MapStyle.STREETS,
            
         center: [-43.206091, -22.920387], // starting position [lng, lat]
         zoom: 11, // starting zoom
            
       });
   </script>
 </body>
 </html>

Replace YOUR_MAPTILER_API_KEY_HERE with your own API key. Make sure to secure the key before you publish it.
The next is up to you. You can center your map wherever you desire (modifying the starting position) and set an appropriate zoom level (modifying the starting zoom) to match your users’ needs. Additionally, you can change the map’s look (by updating the source URL); choose from a range of visually appealing map styles from our extensive MapTiler standard maps, or create your own to truly differentiate your application.
Add event handler for map load event. You will add code to create a GeoJSON source and a vector layer in this handler.
```
 map.on('load', async function() {
    
 });
```
Create GeoJSON source. The following snippet creates GeoJSON source hosted on MapTiler (check out the How to Upload GeoJSON to MapTiler tutorial). Publish the dataset and copy the link to the GeoJSON. Download the Rio de Janeiro sample data.
```
 map.on('load', async function() {
     const geojson = await maptilersdk.data.get('YOUR_MAPTILER_DATASET_ID_HERE');
     map.addSource('rio_cats', {
         type: 'geojson',
         data: geojson
     });
 });
```

Add the vector layer


 map.addLayer({
     'id': 'rio_cats',
     'type': 'fill',
     'source': 'rio_cats',
     'layout': {},
     'paint': {
         'fill-color': '#98b',
         'fill-opacity': 0.8
     }
 });

Complete source code

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>Display a GeoJSON Layer</title>
    <meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no" />
    <script src="https://cdn.maptiler.com/maptiler-sdk-js/v4.1.0/maptiler-sdk.umd.min.js"></script>
    <link href="https://cdn.maptiler.com/maptiler-sdk-js/v4.1.0/maptiler-sdk.css" rel="stylesheet" />
    <style>
        body {
            margin: 0;
            padding: 0;
        }

        #map {
            position: absolute;
            top: 0;
            bottom: 0;
            width: 100%;
        }
    </style>
</head>
<body>
    <div id="map"></div>
    <script>
        maptilersdk.config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';
        const map = new maptilersdk.Map({
            container: 'map', // container's id or the HTML element to render the map
            style: maptilersdk.MapStyle.STREETS,
            center: [-43.206091, -22.920387], // starting position [lng, lat]
            zoom: 11, // starting zoom
        });
        map.on('load', async function () {
            const geojson = await maptilersdk.data.get('YOUR_MAPTILER_DATASET_ID_HERE');
            map.addSource('rio_cats', {
                type: 'geojson',
                data: geojson
            });
            map.addLayer({
                'id': 'rio_cats',
                'type': 'fill',
                'source': 'rio_cats',
                'layout': {},
                'paint': {
                    'fill-color': '#98b',
                    'fill-opacity': 0.8
                }
            });
        });    
    </script>
</body>
</html>