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Leaflet map: reading GeoJSON files dropped-onto
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <title>Leaflet</title> | |
| <meta charset="UTF-8"> | |
| <meta name="viewport" content="width=device-width, initial-scale=1"> | |
| <link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css"> | |
| <script src="https://unpkg.com/[email protected]/dist/leaflet.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> | |
| const par = {lon: 40, lat: 0, zoom: 2, minZoom: 1, maxZoom: 21, map: 'CartoDB', mapDivId: 'map'}; | |
| const pointStyle = {radius:3, color:"#6666aa", opacity:1}; | |
| const otherStyle = {weight:1, color:"#00ff00", opacity:1}; | |
| const OSM_URL = 'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png'; | |
| const OSM_ATTR = 'Map data © 2013 OpenStreetMap contributors'; | |
| const CD_URL = 'http://{s}.basemaps.cartocdn.com/{style}/{z}/{x}/{y}.png'; | |
| const CD_ATTR = '© <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors, © <a href="http://cartodb.com/attributions">CartoDB</a>'; | |
| const baseMaps = { | |
| 'OSM': { | |
| url: OSM_URL, | |
| attribution: OSM_ATTR, | |
| maxNativeZoom: 19 }, | |
| 'CartoDB': { | |
| url: CD_URL, | |
| attribution: CD_ATTR, | |
| maxNativeZoom: 19, | |
| style: 'light_all' }, | |
| }; | |
| Object.keys(baseMaps).forEach((name) => { | |
| const layer = {...baseMaps[name], minZoom: par['minZoom'], maxZoom: par['maxZoom']}; | |
| baseMaps[name] = L.tileLayer(layer.url, layer); | |
| }); | |
| const mapOption = {center: [par['lat'], par['lon']], zoom: par['zoom'], layers: baseMaps[par['map']]}; | |
| const map = L.map(par['mapDivId'], mapOption); | |
| L.control.layers(baseMaps).addTo(map); | |
| L.control.scale().addTo(map); | |
| map.createPane("pane620").style.zIndex = 620; | |
| const dropArea = document.getElementById(par['mapDivId']); | |
| dropArea.ondragover = () => { | |
| return false; | |
| }; | |
| dropArea.ondragend = () => { | |
| return false; | |
| }; | |
| dropArea.ondrop = (event) => { | |
| readFiles(event.dataTransfer.files); | |
| event.preventDefault(); | |
| return false; | |
| }; | |
| const readFiles = (files) => { | |
| const bounds = Array.prototype.map.call(files, readFile); | |
| Promise.all(bounds).then(bounds => {map_fitBounds(bounds);}); | |
| } | |
| const readFile = (file) => { | |
| const {fname, fileExtension} = fileName(file); | |
| return new Promise((resolve, reject) => { | |
| const reader = new FileReader(); | |
| reader.readAsText(file, 'utf-8'); | |
| reader.onload = (event) => { | |
| try { | |
| const result = event.target.result; | |
| const bounds = map_addData(readData(result, fileExtension)); | |
| resolve(bounds); | |
| } catch (err) { | |
| console.log(`${fname}: ${err}`); | |
| } | |
| }; | |
| }); | |
| } | |
| const readData = (result, fileExtension) => { | |
| const data = {"geojson": {"type":"FeatureCollection", "features": []}}; | |
| switch (fileExtension){ | |
| case "json": | |
| case "geojson": | |
| data["geojson"] = JSON.parse(result); | |
| break; | |
| } | |
| return data; | |
| } | |
| const style = (feature) => { | |
| if (feature.geometry.type=="Point" || feature.geometry.type=="MultiPoint") { | |
| return {radius:pointStyle["radius"], fillColor:pointStyle["color"], fillOpacity:pointStyle["opacity"], weight:0, color:"#000000", opacity:0}; | |
| } else { | |
| return {...otherStyle, fillColor: otherStyle["color"], fillOpacity: otherStyle["opacity"]*0.5}; | |
| } | |
| } | |
| const map_addData = (data) => { | |
| const layerOptions = { | |
| style: style, | |
| pointToLayer: (feature, latlng) => { | |
| return L.circleMarker(latlng, {pane: "pane620"}); | |
| }, | |
| }; | |
| const layer = L.geoJSON(data["geojson"], layerOptions); | |
| layer.addTo(map); | |
| return layer.getBounds(); | |
| } | |
| const map_fitBounds = (bounds) => { | |
| const bounds_merged = bounds.pop(); | |
| bounds.forEach(bb => bounds_merged.extend(bb)) | |
| if (bounds_merged.isValid()) map.fitBounds(bounds_merged); | |
| } | |
| const fileName = (file) => { | |
| const fname = file.name; | |
| const fileExtension = fname.split('.').pop(); | |
| return {fname, fileExtension}; | |
| } | |
| </script> | |
| </body> | |
| </html> |
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