how to make a while loop in nodejs to be a series - mysql

Question

My Nodejs Code:
i am trying to download files (excel) from a server and parse those excel files and from that data store only required data into mysql database i may download multiple files for that my loop may get interrupted so how to do my below code to run in a series of synchronous way
var r=0;
if (issue.fields.attachment != '') {
while (typeof issue.fields.attachment[r] != "undefined") {
if (typeof issue.fields.attachment[r].content != "undefined") {
var url = issue.fields.attachment[r].content;
request({
method: "GET",
"url": url,
"headers": { "Content-Type": "application/json", }
}, function(err, data, body) {
console.log('file downloading');
}).pipe(fs.createWriteStream('file.xlsx'));
console.log('file downloaded');
parseXlsx('file.xlsx', function(err, data) {
var i, j, k = 1, l = 0, m = 0, n = 0;
console.log('parseXlsx cmpleted');
while (data[i] != undefined) {
if (data[i][j] != '' || data[i][k] != '' || data[i][l] != '') {
var query = connection.query('insert into IP values ("' + data[i][j] + '","' + data[i][k] + '","' + data[i][l] + '","' + data[i][m] + '")',
function(error, results, fields) {
});
}
i++;
}
});
r++;
console.log('rvalue' + r);
}
}
}

Answer 1

I (very quickly, so it probably has errors) rewrote this using async.forEachOfSeries to iterate over your attachments. I used async.forEachOf for the database writes as I don't see a need for them to be in series.
var async = require('async');
if (issue.fields.attachment != '') {
async.forEachOfSeries(issue.fields.attachment,function(attachment,r,callback){
if (typeof issue.fields.attachment[r].content != "undefined") {
var url = issue.fields.attachment[r].content;
var ws = fs.createWriteStream('file.xlsx');
request({ method: "GET", "url": url, "headers": { "Content-Type": "application/json" }
}, function(err, data, body) {
console.log('file downloading');
}).pipe(ws);
ws.on('finish',function() {
console.log('file downloaded');
parseXlsx('file.xlsx', function (err, data) {
var i, j, k = 1, l = 0, m = 0, n = 0;
for (i = 0; i < 15; i++) {
for (j = 0; j < 15; j++) {
if (regex.test(data[i][j])) {
k = 0;
break;
}
}
if (k == 0)
break;
}
for (k = 0; k < 15; k++) {
if (regex1.test(data[i][k])) {
break;
}
}
for (l = 0; l < 15; l++) {
if (regex2.test(data[i][l])) {
break;
}
}
for (m = 0; m < 15; m++) {
if (regex2.test(data[i][m])) {
break;
}
}
i = i + 1;
console.log('parseXlsx completed');
async.forEachOf(data,function(row,i,_callback){
if(i===0)return _callback();
if (data[i][j] != '' || data[i][k] != '' || data[i][l] != '') {
var query = connection.query('insert into IP values ("' + data[i][j] + '","' + data[i][k] + '","' + data[i][l] + '","' + data[i][m] + '")',
function (error, results, fields) {
if(error){
//Decide if you want to stop writing rows if one insert fails, if so uncomment next line
//return _callback(error);
}
return _callback();
});
}
},function(err){
if(err){
//decide if you want to stop the whole process if the database errored, if so, uncomment next line
//return callback(err);
}
callback();
});
});
});
ws.on('error',function(err) {
//There was an error writing the file to disk, but I assume you want to continue anyway so I'm calling callback()
//If you want to stop processing, call callback(new Error('Failed writing to disk'));
return callback();
});
}
});
}