Join local JSON data with vector tile geometries
This example styles a choropleth map by merging local JSON data with vector tile geometries.
It uses the match
expression to join the Mapbox Countries vector tileset with local JSON data by using a three-letter ISO country code as the lookup key for the country shape.
<!DOCTYPE html><html><head><meta charset="utf-8"><title>Join local JSON data with vector tile geometries</title><meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no"><link href="https://api.mapbox.com/mapbox-gl-js/v2.14.1/mapbox-gl.css" rel="stylesheet"><script src="https://api.mapbox.com/mapbox-gl-js/v2.14.1/mapbox-gl.js"></script><style>body { margin: 0; padding: 0; }#map { position: absolute; top: 0; bottom: 0; width: 100%; }</style></head><body><div id="map"></div><script> // TO MAKE THE MAP APPEAR YOU MUST // ADD YOUR ACCESS TOKEN FROM // https://account.mapbox.com mapboxgl.accessToken = 'YOUR_MAPBOX_ACCESS_TOKEN';const map = new mapboxgl.Map({container: 'map',// Choose from Mapbox's core styles, or make your own style with Mapbox Studiostyle: 'mapbox://styles/mapbox/light-v11',center: [12, 50],zoom: 2.2}); // Data: UN Human Development Index 2017 Europe extract// Source: https://ourworldindata.org/human-development-indexconst data = [{ 'code': 'ROU', 'hdi': 0.811 },{ 'code': 'RUS', 'hdi': 0.816 },{ 'code': 'SRB', 'hdi': 0.787 },{ 'code': 'SVK', 'hdi': 0.855 },{ 'code': 'SVN', 'hdi': 0.896 },{ 'code': 'ESP', 'hdi': 0.891 },{ 'code': 'SWE', 'hdi': 0.933 },{ 'code': 'CHE', 'hdi': 0.944 },{ 'code': 'HRV', 'hdi': 0.831 },{ 'code': 'CZE', 'hdi': 0.888 },{ 'code': 'DNK', 'hdi': 0.929 },{ 'code': 'EST', 'hdi': 0.871 },{ 'code': 'FIN', 'hdi': 0.92 },{ 'code': 'FRA', 'hdi': 0.901 },{ 'code': 'DEU', 'hdi': 0.936 },{ 'code': 'GRC', 'hdi': 0.87 },{ 'code': 'ALB', 'hdi': 0.785 },{ 'code': 'AND', 'hdi': 0.858 },{ 'code': 'AUT', 'hdi': 0.908 },{ 'code': 'BLR', 'hdi': 0.808 },{ 'code': 'BEL', 'hdi': 0.916 },{ 'code': 'BIH', 'hdi': 0.768 },{ 'code': 'BGR', 'hdi': 0.813 },{ 'code': 'MKD', 'hdi': 0.757 },{ 'code': 'MLT', 'hdi': 0.878 },{ 'code': 'MDA', 'hdi': 0.7 },{ 'code': 'MNE', 'hdi': 0.814 },{ 'code': 'NLD', 'hdi': 0.931 },{ 'code': 'NOR', 'hdi': 0.953 },{ 'code': 'POL', 'hdi': 0.865 },{ 'code': 'PRT', 'hdi': 0.847 },{ 'code': 'HUN', 'hdi': 0.838 },{ 'code': 'ISL', 'hdi': 0.935 },{ 'code': 'IRL', 'hdi': 0.938 },{ 'code': 'ITA', 'hdi': 0.88 },{ 'code': 'LVA', 'hdi': 0.847 },{ 'code': 'LIE', 'hdi': 0.916 },{ 'code': 'LTU', 'hdi': 0.858 },{ 'code': 'LUX', 'hdi': 0.904 },{ 'code': 'UKR', 'hdi': 0.751 },{ 'code': 'GBR', 'hdi': 0.922 }]; map.on('load', () => {// Add source for country polygons using the Mapbox Countries tileset// The polygons contain an ISO 3166 alpha-3 code which can be used to for joining the data// https://docs.mapbox.com/vector-tiles/reference/mapbox-countries-v1map.addSource('countries', {type: 'vector',url: 'mapbox://mapbox.country-boundaries-v1'}); // Build a GL match expression that defines the color for every vector tile feature// Use the ISO 3166-1 alpha 3 code as the lookup key for the country shapeconst matchExpression = ['match', ['get', 'iso_3166_1_alpha_3']]; // Calculate color values for each country based on 'hdi' valuefor (const row of data) {// Convert the range of data values to a suitable colorconst green = row['hdi'] * 255;const color = `rgb(0, ${green}, 0)`; matchExpression.push(row['code'], color);} // Last value is the default, used where there is no datamatchExpression.push('rgba(0, 0, 0, 0)'); // The mapbox.country-boundaries-v1 tileset includes multiple polygons for some// countries with disputed borders. The following expression filters the// map view to show the "US" perspective of borders for disputed countries.// Other world views are available, for more details, see the documentation// on the "worldview" feature property at// https://docs.mapbox.com/data/tilesets/reference/mapbox-countries-v1/#--polygon---worldview-textconst WORLDVIEW = "US";const worldview_filter = [ "all", [ "==", ["get", "disputed"], "false" ], [ "any", [ "==", "all", ["get", "worldview"] ], [ "in", WORLDVIEW, ["get", "worldview"] ] ] ]; // Add layer from the vector tile source to create the choropleth// Insert it below the 'admin-1-boundary-bg' layer in the stylemap.addLayer({'id': 'countries-join','type': 'fill','source': 'countries','source-layer': 'country_boundaries','paint': {'fill-color': matchExpression},'filter': worldview_filter},'admin-1-boundary-bg');});</script> </body></html>