Drop multiple geojson files on a mapbox gl js map

README.md

Experimental work with mapbox gl js, web workers and geojsonhint to create new layers by drag and dropping geojson data.

app.css

body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }

app.js

// mapbox gl init
mapboxgl.accessToken = 'pk.eyJ1IjoidW5lcGdyaWQiLCJhIjoiY2lzZnowenUwMDAzdjJubzZyZ3R1bjIzZyJ9.uyP-RWjY-94qCVajU0u8KA';
var map = new mapboxgl.Map({
    container: 'map',
    style: 'mapbox://styles/mapbox/dark-v9',
    center: [-14.66,-23.64],
    zoom: 3
});

// object to hold geojson
var data = {};

// test if file api is available
if (window.File && window.FileReader && window.FileList && window.Blob) {


    // handle read geojson
    // Update progress
    var updateProgress = function(theFile) {
        return function(e) {
            // evt is an ProgressEvent. 100/2 as loading is ~ half the process
            if (e.lengthComputable) {
                var percentLoaded = Math.round((e.loaded / e.total) * 50);
                progressScreen(
                    true,
                    theFile.name,
                    percentLoaded,
                    theFile.name + " loading (" + percentLoaded + "%)"
                );
            }
        };
    };
    // init progress bar
    var startProgress = function(theFile) {
        return function(e) {
            progressScreen(
                true,
                theFile.name,
                0,
                theFile.name + " init .. "
            );
        };
    };
    // on error, set progress to 100 (remove it)
    var errorProgress = function(theFile) {
        return function(e) {
            progressScreen(
                true,
                theFile.name,
                100,
                theFile.name + "stop .. "
            );
        };
    };

    // handle worker
    var startWorker = function(theFile) {
        return function(e) {
            // Create a worker to handle this file
            var w = new Worker("handleReadJson.js");

            // parse file content before passing to worker.
            var gJson = JSON.parse(e.target.result);

            // Message to pass to the worker
            var res = {
                json: gJson,
                fileName: theFile.name
            };

            // handle message received
            w.onmessage = function(e) {
                var m = e.data;
                if ( m.progress ) {
                    progressScreen(
                        true,
                        theFile.name,
                        m.progress,
                        theFile.name + ": " + m.message
                    );
                }

               // send alert for errors message
                if( m.errorMessage ){
                  alert(m.errorMessage);
                }

                // If extent is received
                if (m.extent) {
                    map.fitBounds(m.extent);
                }

                // If layer is valid and returned
                if (m.layer) {
                  try {
                    progressScreen(
                        true,
                        theFile.name,
                        100,
                        theFile.name + " done"
                    );
                    // add source to map
                    map.addSource(m.id, {
                        "type": "geojson",
                        "data": gJson
                    });
                    // add layer
                    map.addLayer(m.layer,"place-village");
                    // set progress to max
                    data[m.id] = gJson;
                  }
                  catch(err){
                    alert(err);
                  }
                  // close worker
                   w.terminate();
                }

            };

            // launch process
            try {
            w.postMessage(res);
            }catch(err){
              alert("An error occured, quick ! check the console !");
              console.log({
                res : res,
                err : err
              });
            }
        };
    };

    var updateLayerList = function(theFile) {
        return function(e) {};
    };
    // handle drop event
    var handleDropGeojson = function(evt) {
        evt.stopPropagation();
        evt.preventDefault();
        var files = evt.dataTransfer.files;

        var nFiles = files.length;
        var incFile = 100 / nFiles;
        var progressBar = 0;

        // In case of multiple file, loop on them
        for (var i = 0; i < nFiles; i++) {

            f = files[i];

            // Only process geojson files. Validate later.
            if (f.name.toLowerCase().indexOf(".geojson") == -1) {
                alert(f.name + " not supported");
                continue;
            }
            // get a new reader
            var reader = new FileReader();
            // handle events
            reader.onloadstart = (startProgress)(f);
            reader.onprogress = (updateProgress)(f);
            reader.onerror = (errorProgress)(f);
            reader.onload = (startWorker)(f);
            reader.onloadend = (updateLayerList)(f);
            // read the geojson
            reader.readAsText(f);
        }
    };
    var handleDragOver = function(evt) {
        evt.stopPropagation();
        evt.preventDefault();
        evt.dataTransfer.dropEffect = 'copy'; // Explicitly show this is a copy.
    };

    // Set events
    mapEl = document.getElementById("map");
    mapEl.addEventListener('dragover', handleDragOver, false);
    mapEl.addEventListener('drop', handleDropGeojson, false);


} else {
    alert('The File APIs are not fully supported in this browser.');
}

handleReadJson.js

// Importation of helpers
importScripts(
    "https://npmcdn.com/geojsonhint@latest/geojsonhint.js",
    "turf_bbox.js",
    "helpers.js"
    );

// Inital message
postMessage({
  progress: 0,
  message: "start"
});


// handle message send from the main thread
onmessage = function(e) {
  try {

    /**
     * Initialisation : set local helper and variables
     */

    // init variables
    var errorMsg = "";
    var warningMsg = "";
    var dat = e.data;
    var gJson = dat.json;
    var fileName = dat.fileName;

    // set basic timing function
    timerVal = 0;

    // start timer
    var timerStart = function() {
      timerVal = new Date();
    };

    // give intermediate time, reset timer
    var timerLap = function() {
      var lap = new Date() - timerVal;
      timerStart();
      return lap;
    };

    // printable version of timerLaè
    var timerLapString = function() {
      return " " + timerLap() + " ms ";
    };

    // start timer
    timerStart();

    /**
     * validation : geojson validation with geojsonhint
     */

    // Validation. Is that a valid geojson ?
    var messages = geojsonhint.hint(gJson);
    // extract errors
    var errors = messages.filter(function(x){
      return x.level == "error";
    });
    // extract message
    var warnings = messages.filter(function(x){
      return x.level == "message";
    });

    // set a message with summary
    var logMessage = " geojson validation " +
      " n errors = " + errors.length +
      " n warnings = " + warnings.length + " done in" +
      timerLapString();

    console.log(fileName + ":" + logMessage);

    // send message
    postMessage({
      progress: 60,
      message: logMessage
    });

    // validation : warnings
    if (warnings.length > 0) {
      warningMsg = warnings.length + " warning message(s) found. Check the console for more info";
      postMessage({
        progress: 75,
        msssage: warningMsg
      });
      warnings.forEach(function(x) {
        console.log({file:fileName,warnings:x});
      });
    }
    // varlidation: errors
    if (errors.length > 0) {
      errorMsg = errors.length + " errors found. check the console for more info";
      postMessage({
        progress: 100,
        msssage: errorMsg,
        errorMessage: errorMsg
      });

      errors.forEach(function(x) {
        console.log({file:fileName,errors:x});
      });

      return;
    }


    /**
     * Get extent : get extent using a Turf bbox
     */

    var extent = turf.bbox(gJson);

    // Quick extent validation 
    if (
        extent[0] > 180 || extent[0] < -180 ||
        extent[1] > 89 || extent[1] < -89 ||
        extent[2] > 180 || extent[2] < -180 ||
        extent[3] > 89 || extent[3] < -89
       ) {
      errorMsg = fileName + " : extent seems to be out of range: " + extent;

      postMessage({
        progress: 100,
        msssage: errorMsg,
        errorMessage: errorMsg
      });

      console.log({
        "errors": errorMsg
      });
      return;
    }

    postMessage({
      progress: 80,
      message: " extent found in " + timerLapString()
    });


    /**
     * Avoid multi type : we don't handle them for now
     */

    var geomType = [];
    if( gJson.features ){
      // array of types in data
      geomTypes  = gJson.features
        .map(function(x){
          return typeSwitcher[x.geometry.type];
        })
      .filter(function(v,i,s){
        return s.indexOf(v) === i;
      });
    }else{
      geomTypes = [typeSwitcher[gJson.geometry.type]];
    }


    postMessage({
      progress: 90,
      message: " geom types =" + geomTypes + " found in " + timerLapString()
    });

    // if more than one type, return an error
    if ( geomTypes.length>1) {
      var msg = "Multi geometry not yet implemented";

      postMessage({
        progress: 100,
        msssage: msg,
        errorMessage: fileName + ": " + msg
      });

      console.log({
        "errors": fileName + ": " + msg + ".(" + geomTypes + ")"
      });
      return;
    }


    /**
     * Set default for a new layer
     */

    // Set random id for source and layer
    var id = "mgl_drop_" + randomString(5) + "_" + fileName ;
    // Set random color
    var ran = Math.random();
    var colA = randomHsl(0.1, ran);
    var colB = randomHsl(0.5, ran);

    // Set default type from geojson type
    var typ = geomTypes[0];

    // Set up default style
    var dummyStyle = {
      "circle": {
        "id": id,
        "source": id,
        "type": typ,
        "paint": {
          "circle-color": colA
        }
      },
      "fill": {
        "id": id,
        "source": id,
        "type": typ,
        "paint": {
          "fill-color": colA,
          "fill-outline-color": colB
        }
      },
      "line": {
        "id": id,
        "source": id,
        "type": typ,
        "paint": {
          "line-color": colA,
          "line-width": 10
        }
      }
    };


    postMessage({
      progress: 99,
      message: "Add layer",
      id: id,
      extent: extent,
      layer: dummyStyle[typ]
    });
  }

  catch(err) {
    console.log(err);
    postMessage({
      progress: 100,
      errorMessage : "An error occured, yey ! Quick, check the console !"
    });
  }
};

helpers.js

/**
 * Generate a random string of the given length
 * @param {integer} n Number of character
 * @return {string} random string
 */
var randomString = function(n) {
    var result = "";
    if (!n) n = 5;
    var characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    for (var i = 0; i < n; i++)
        result += characters.charAt(Math.floor(Math.random() * characters.length));
    return result;
};
/**
 * Generate a random hsla color string, with fixed saturation and lightness
 * @param {number} opacity opacity from 0 to 1
 * @param {number} random value from 0 to 1
 * @param {number} saturation from 0 to 100
 * @param {number} lightness from 0 to 100
 */
var randomHsl = function(opacity, random, saturation, lightness) {
    if (!opacity) opacity = 1;
    if (!saturation) saturation = 100;
    if (!lightness) lightness = 50;
    if (!random) random = Math.random();
    res = "hsla(" + (random * 360) +
        ", " + saturation + "% " +
        ", " + lightness + "% " +
        ", " + opacity + ")";
    return res;
};

/**
 * Remove multiple layers by prefix
 * @param {object} map Map object
 * @param {string} prefix Prefix to search for in layers, if something found, remove it
 * @return {array} List of removed layer 
 */
var removeLayersByPrefix = function(map, prefix) {
    var result = [];

    if (map) {
        // no method to get all layers ?
        var layers = map.style._layers;
        for (var l in layers) {
            if (l.indexOf(prefix) > -1) {
                map.removeLayer(l);
                result.push(l);
            }
        }
    }

    return result;
};

/**
 * Create and manage multiple progression bar
 * @param {boolean} enable Enable the screen 
 * @param {string} id Identifier of the given item
 * @param {number} percent Progress bar percentage
 * @param {string} text Optional text
 */
var progressScreen = function(enable, id, percent, text ) {

    lScreen = document.getElementsByClassName("loading-screen")[0];

    if (!enable) {
        if (lScreen) lScreen.remove();
        return;
    }

    if (!id || !percent || !text) return;

    if (!lScreen && enable) {
        lBody = document.getElementsByTagName("body")[0];
        lScreen = document.createElement("div");
        lScreen.className = "loading-screen";
        lScreenContainer = document.createElement("div");
        lScreenContainer.className = "loading-container";
        lScreen.appendChild(lScreenContainer);
        lBody.appendChild(lScreen);
    }

    lItem = document.getElementById(id);

    if (!lItem) {
        lItem = document.createElement("div");
        lItem.className = "loading-item";
        lItem.setAttribute("id", id);
        pBarIn = document.createElement("div");
        pBarIn.className = "loading-bar-in";
        pBarOut = document.createElement("div");
        pBarOut.className = "loading-bar-out";
        pBarTxt = document.createElement("div");
        pBarTxt.className = "loading-bar-txt";
        pBarOut.appendChild(pBarIn);
        lItem.appendChild(pBarTxt);
        lItem.appendChild(pBarOut);
        lScreenContainer.appendChild(lItem);
    } else {
        pBarIn = lItem.getElementsByClassName("loading-bar-in")[0];
        pBarTxt = lItem.getElementsByClassName("loading-bar-txt")[0];
    }

    if (percent >= 100) {
        lItem = document.getElementById(id);
        if (lItem) lItem.remove();
    } else {
        pBarIn.style.width = percent + "%";
        pBarTxt.innerHTML = text;
    }

    lItems = lScreenContainer.getElementsByClassName("loading-item");

    if (lItems.length === 0) progressScreen(false);

};



// geojson type to mapbox gl type
var typeSwitcher = {
    "Point": "circle",
    "MultiPoint": "line",
    "LineString": "line",
    "MultiLineString": "line",
    "Polygon": "fill",
    "MultiPolygon": "fill",
    "GeometryCollection": "fill"
};

index.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset='utf-8' />
    <title>Drop geojson</title>
    <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
    <meta http-equiv="cache-control" content="Public">
    <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.36.0/mapbox-gl.css' rel='stylesheet' />
    <link href='progress.css' rel='stylesheet' />
    <link href='app.css' rel='stylesheet' />
  </head>
  <body>
    <div id='map'></div>
    <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.36.0/mapbox-gl.js'></script>
    <script src='helpers.js'></script>
    <script src='app.js'></script>
  </body>
</html>

progress.css

.loading-screen {
  background-color : rgba(47,47,47,0.6);
  top: 0px;
  width: 100%;
  bottom:0px;
  display: block;
  position:absolute;
}

.loading-container {
  font-family : "Lucida Console", Monaco, monospace;
  color: #0f0;
  position:absolute;
  width: 40%;
  left: 50%;
  padding: 10px;
}

.loading-item {
    padding: 5px;
    width: 99%;
}

.loading-bar-out { 
  height:5px;
  width:100%;
  border:1px solid #0f0;
}

.loading-bar-in {
  width:0px;
  height:100%;
  background-color: #0f0;
}

.loading-bar-txt {
  font-size: 14px;
}

turf_bbox.js

(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.turf = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
var each=require("turf-meta").coordEach;module.exports=function(r){var e=[1/0,1/0,-(1/0),-(1/0)];return each(r,function(r){e[0]>r[0]&&(e[0]=r[0]),e[1]>r[1]&&(e[1]=r[1]),e[2]<r[0]&&(e[2]=r[0]),e[3]<r[1]&&(e[3]=r[1])}),e};
},{"turf-meta":2}],2:[function(require,module,exports){
function coordEach(e,o,t){var r,n,c,u,l,p,a,i,f,h,d=0,s="FeatureCollection"===e.type,y="Feature"===e.type,g=s?e.features.length:1;for(r=0;r<g;r++)for(f=s?e.features[r].geometry:y?e.geometry:e,h="GeometryCollection"===f.type,a=h?f.geometries.length:1,u=0;u<a;u++)if(p=h?f.geometries[u]:f,i=p.coordinates,d=!t||"Polygon"!==p.type&&"MultiPolygon"!==p.type?0:1,"Point"===p.type)o(i);else if("LineString"===p.type||"MultiPoint"===p.type)for(n=0;n<i.length;n++)o(i[n]);else if("Polygon"===p.type||"MultiLineString"===p.type)for(n=0;n<i.length;n++)for(c=0;c<i[n].length-d;c++)o(i[n][c]);else{if("MultiPolygon"!==p.type)throw new Error("Unknown Geometry Type");for(n=0;n<i.length;n++)for(c=0;c<i[n].length;c++)for(l=0;l<i[n][c].length-d;l++)o(i[n][c][l])}}function coordReduce(e,o,t,r){return coordEach(e,function(e){t=o(t,e)},r),t}function propEach(e,o){var t;switch(e.type){case"FeatureCollection":for(t=0;t<e.features.length;t++)o(e.features[t].properties);break;case"Feature":o(e.properties)}}function propReduce(e,o,t){return propEach(e,function(e){t=o(t,e)}),t}function featureEach(e,o){if("Feature"===e.type)return o(e);if("FeatureCollection"===e.type)for(var t=0;t<e.features.length;t++)o(e.features[t])}function coordAll(e){var o=[];return coordEach(e,function(e){o.push(e)}),o}module.exports.coordEach=coordEach,module.exports.coordReduce=coordReduce,module.exports.propEach=propEach,module.exports.propReduce=propReduce,module.exports.featureEach=featureEach,module.exports.coordAll=coordAll;
},{}],3:[function(require,module,exports){
module.exports={bbox:require("turf-bbox")};
},{"turf-bbox":1}]},{},[3])(3)
});