如何用Javascript写入文件？

Question

我已经编写了将JSON写入文件并下载的代码。除无法将出现在浏览器和控制台中的JSON数据写入文件外，其他所有文件均显示良好。 JSON数据（dataStr）在下载的文件中显示为未定义。 这是代码的摘录：

function exportToJsonFile(obj) {

  let dataStr = JSON.stringify(obj);              // Converts object into string
  console.log('dataStr type: '+ typeof dataStr);  // String                          
  console.log(dataStr);                           // Data appears in console
  $('#dataStr').text(dataStr);                    // Data appears in browser

  let text = 'JSON data: '+ dataStr;                                                  // 'text' is written to file but dataStr cannot be written to file 
  console.log('text type: '+ typeof text);        // String

  let dataUri = 'data:application/json;charset=utf-8,'+ encodeURIComponent(text);     // write to file

  let exportFileDefaultName = 'raingeojson.json';                                     // set default file name
  let linkElement = document.createElement('a');                                      // create link element
  linkElement.setAttribute('href', dataUri);                                          // create href = dataUri
  linkElement.setAttribute('download', exportFileDefaultName);                        // create link of the download to the button
  linkElement.click();                                                                // create click
}

编辑：这是将值传递给obj的函数。

$.getJSON("https://api.data.gov.sg/v1/environment/rainfall?date=2019-07-03",
   rainfall = function(data_rainfall){
    console.log(data_rainfall);        

  var apiGeoLoc = { type: "FeatureCollection", features: []};
  apiGeo = { type: "FeatureCollection", features: []};

for (var i in  data_rainfall.items){
    for (var j in data_rainfall.items[i].readings){
        var date_t = data_rainfall.items[i].timestamp.split('T');
        var date = date_t[0];
        var time = date_t[1].split(':');
        var hour_string = time[0];
        var hour = parseInt(hour_string);

    apiGeo.features.push({
        "type":"Feature",
        "properties": {
            "timestamp": data_rainfall.items[i].timestamp,
            "date": date,
            "Hour": hour,
            "id": data_rainfall.items[i].readings[j].station_id,
            "value": data_rainfall.items[i].readings[j].value
        },
        "geometry":{}
     });
}}
    for (var i in  data_rainfall.metadata.stations){
    apiGeoLoc.features.push({
        "type":"Feature",
        "properties": {
            "station_name": data_rainfall.metadata.stations[i].name,
            "id": data_rainfall.metadata.stations[i].id
        },
        "geometry":{
            "type": "Point",
            "coordinates": [data_rainfall.metadata.stations[i].location.longitude, data_rainfall.metadata.stations[i].location.latitude]
        }
    });
    }
     for(var a in apiGeo.features){
      for (var b in apiGeoLoc.features){
        if (apiGeo.features[a].properties.id===apiGeoLoc.features[b].properties.id){            
            for(var attr in apiGeoLoc.features[b].properties){                                  //create new attribute to insert properties
                apiGeo.features[a].properties[attr] = apiGeoLoc.features[b].properties[attr];   //apiGeo takes apiGeoLoc attributes
            }
             for(var coord in apiGeoLoc.features[b].geometry){
                 apiGeo.features[a].geometry[coord] = apiGeoLoc.features[b].geometry[coord];    //apiGeo takes apiGeoLoc coordinates
        }
    }
}} 
console.log(apiGeo);
apiGeof = apiGeo.features;
exportToJsonFile(apiGeof);
});