create csv file javascript

1 $("#download_1").click(function() {
2var json_pre = '[{"Id":1,"UserName":"Sam Smith"},{"Id":2,"UserName":"Fred Frankly"},{"Id":1,"UserName":"Zachary Zupers"}]';
3var json = $.parseJSON(json_pre);
4
5var csv = JSON2CSV(json);
6var downloadLink = document.createElement("a");
7var blob = new Blob(["\ufeff", csv]);
8var url = URL.createObjectURL(blob);
9downloadLink.href = url;
10downloadLink.download = "data.csv";
11
12document.body.appendChild(downloadLink);
13downloadLink.click();
14document.body.removeChild(downloadLink);
15});

1function JSON2CSV(objArray) {
2    var array = typeof objArray != 'object' ? JSON.parse(objArray) : objArray;
3    var str = '';
4    var line = '';
5
6    if ($("#labels").is(':checked')) {
7        var head = array[0];
8        if ($("#quote").is(':checked')) {
9            for (var index in array[0]) {
10                var value = index + "";
11                line += '"' + value.replace(/"/g, '""') + '",';
12            }
13        } else {
14            for (var index in array[0]) {
15                line += index + ',';
16            }
17        }
18
19        line = line.slice(0, -1);
20        str += line + '\r\n';
21    }
22
23    for (var i = 0; i < array.length; i++) {
24        var line = '';
25
26        if ($("#quote").is(':checked')) {
27            for (var index in array[i]) {
28                var value = array[i][index] + "";
29                line += '"' + value.replace(/"/g, '""') + '",';
30            }
31        } else {
32            for (var index in array[i]) {
33                line += array[i][index] + ',';
34            }
35        }
36
37        line = line.slice(0, -1);
38        str += line + '\r\n';
39    }
40    return str;
41}

1const file1 = 'one.csv';
2const file2 = 'two.csv';
3const stream = fs.createReadStream(file1);
4const stream2 = fs.createReadStream(file2);
5const fileData1 = [];
6const fileData2 = [];
7
8const file1Promise = new Promise((resolve) => {
9  csv
10      .parseFile(file1, {headers: true})
11      .on('data', function(data) {
12        fileData1.push(data);
13      })
14      .on('end', function() {
15        console.log('done');
16        resolve();
17      });
18});
19
20const file2Promise = new Promise((resolve) => {
21  csv
22      .parseFile(file2, {headers: true})
23      .on('data', function(data) {
24        fileData2.push(data);
25      })
26      .on('end', function() {
27        console.log('done');
28        resolve();
29      });
30});
31
32Promise.all([
33  file1Promise,
34  file2Promise,
35])
36    .then(() => {
37      const fileData3 = fileData1.concat(fileData2);
38      console.log(fileData3);
39
40      const csvStream = csv.format({headers: true});
41      const writableStream = fs.createWriteStream('outputfile.csv');
42
43      writableStream.on('finish', function() {
44        console.log('DONE!');
45      });
46
47      csvStream.pipe(writableStream);
48      fileData3.forEach((data) => {
49        csvStream.write(data);
50      });
51      csvStream.end();
52    });
53