How to create a countries map with your own data

This tutorial demonstrates the process of merging your own personalized data with the MapTiler Countries dataset, allowing you to create a choropleth map. The MapTiler Countries dataset primarily consists of information regarding the administrative divisions of countries and their territories around the world.

For this specific example, we will be creating a choropleth map that showcases the population of some European countries.

Copy the following code, paste it into your favorite text editor, and save it as a .html file.
Install the npm package.
Include the CSS file.

If you have a bundler that can handle CSS, you can import the CSS or include it with a <link> in the head of the document via the CDN
Include the following code in your JavaScript file (Example: app.js).
Replace YOUR_MAPTILER_API_KEY_HERE with your actual MapTiler API key.
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 vector source and a vector layer in this handler.
Create vector source. The following snippet creates vector source for the MapTiler Countries dataset.
Get the id of the first symbol layer. We want to include the vector layer below the map labels. That means we need to know the id of the first symbol layer so we can include the vector layer before this layer.
Add the vector layer. We need to include firsSymbolId to the map.addLayer function to display the vector under the maps labels
Filter the data to only show the countries. Add a filter to the layer to only display level 0 items.
Prepare your data. Each feature in the dataset has its own identification for pairing. You need to mark your data with the same identifiers as is stored by features. We will use the iso_n3 identifier for countries. Alternatively, you can use one of the properties: name, country codes (ISO A2), or wiki data-id. Check out the Countries dataset schema to see the available fields.
Join the data to coresponding features. Use querySourceFeatures to get all features from the layer for visualization. We are also filtering for all countries with ['==', 'level', 0] using style expressions. The second part of the following code goes throw these features and adds attributes from our data array (vizData) to relevant features.
Create a function that validates that the country dataset is loaded to call the setStates function.
Add event handler for map data event. Call the afterLoad function
Create a choropleth map based on the population attribute. Change the fill-color property of the layer.
Display a popup when clicking on the vector layer and show the information of the age attribute.
To make our map more user friendly, we will change the cursor when hovering over a geometry in the vector layer to indicate to the user that they can click on it.