This topic describes how to change data on the isosurface layer with the timeline. An API or a database is needed to obtain data from different monitoring sites during different periods of time.

We recommend that you write an API.
  • Request address: /aqi
  • Request method: GET
  • Request parameter:
    • Parameter: date
    • Parameter type: string, for example, 2017012722. The format is YYYYmmDDHH.
  1. Process all the downloaded data. Node.js provides a glob module to process all data in the directory in batches.
    var fs = require('fs');
var csv = require("fast-csv");
var glob = require('glob');
var mapdata = require('. /Longitude and latitude mapping in the site list.json');
glob(". /Site_20170101-20170202/*.csv", function (err, files) {
files.forEach(function (file) {
 var filename = file.replace(/^. *[\\\/]/, '').split('.')[0] .split('_')[2];
 var datas = {};
 csv
   .fromPath(file, { headers: true, objectMode: true })
   .on("data", function (data) {
     if (data.type === 'AQI') {
       datas[data.hour] = [];
       for (var key in data) {
         if (mapdata[key]) {
           datas[data.hour].push({
             name: mapdata[key].name,
             value: +data[key],
             code: mapdata[key].code,
             city: mapdata[key].city,
             lng: +mapdata[key].lng,
             lat: +mapdata[key].lat
           })
         }
       }
     }
   })
   .on("end", function () {
     fs.writeFile('./data/' + filename + '.json', JSON.stringify(datas));
     console.log("done");
   });
});
});
    The result is as follows.

  2. Use the glob module to integrate the data. Use the file name (which is a date) as the key, and the corresponding content as the value. Then, you will obtain an integration file named all.json.
    //The following method is not suitable to process data in large scale.
var fs = require('fs');
var csv = require("fast-csv");
var glob = require('glob');
glob("./data/*.json", function (err, files) {
var datas = {};
files.forEach(function (file) {
 var filename = file.replace(/^. *[\\\/]/, '').split('.')[0];
 datas[filename] = require(file);
});
fs.writeFile('./data/all.json', JSON.stringify(datas));
console.log('done');
});
  3. Use the express framework of Node.js to initialize an express project, and add an API according to the preceding API requirements.

    Note To avoid cross-domain requests, you can add a cors module to the app.js file.

  4. After processing the API, run the npm start command to test the API.