Node js send an email with pdf as attachement synchronously - node.js

Question

Task : Get query from database => generate multiple pdf => send in mail attachment via node js
Problem: the problem here is before pdfs are generated my sendMail() function called. So how to call sendMail function only after all pdfs generated?
pdfs = [];
// Pdf generate code
var generatePdf = function (rows) {
return new Promise(function (resolve, reject) {
for (var i = 0; i < rows.length; i++) {
html = ejs.renderFile(
'views/voucher.ejs',
{
voucher: rows[i]
},
function (error, success) {
if (error) {
console.log(error);
} else {
var pdf_path = '/srv/ voucher/uploads/voucher/' + Math.random().toString(36).substring(7) + '.pdf';
htmlToPdf.convertHTMLString(success, pdf_path, function (error, success) {
if (error) {
console.log('Oh noes! Errorz!');
console.log(error);
} else {
pdfs.push(pdf_path);
console.log("Single");
console.log(pdfs);
console.log('Woot! Success!');
}
});
}
});
}
resolve();
});
}
// send mail code
var sendMail = function () {
new Promise(function (resolve, reject) {
console.log("All" + pdfs);
pdfs.forEach(function (value, key) {
// mail sending code
});
});
};
var findVoucherAndSendMail = function () {
return new Promise(function (resolve, reject) {
var query = con.query('SELECT * FROM voucher limit 20', function selectAll(err, rows, fields) {
if (err) {
throw err;
}
resolve(rows);
});
});
};
findVoucherAndSendMail().then(function (fromResolve) {
return generatePdf(fromResolve);
}).then(function () {
return sendMail();
}).catch(function () {
});

Answer 1

Your problem is link to an asynchronous behavior in your for loop when generating pdf.
Your promise is resolved before your pdfs are generated.
You should use Promise.all to wait for generation completion.
function generatePdf(rows) {
return Promise.all(rows.map(row => asyncPdfGeneration(row));
}
function asyncPdfGeneration(row) {
return new Promise(function (resolve, reject) {
...generate pdf
resolve(pdf);
}
}

Answer 2

The 2nd 'then' is on your function findVoucherAndSendMail(), so both generatePdf() and sendMail() will fire once findVoucherAndSendMail() is finished.
Place the 2nd 'then' on generatePdf()
findVoucherAndSendMail().then(function (fromResolve) {
return generatePdf(fromResolve).then(function () {
return sendMail();
});
}).catch(function () {
});
edit
Did you try: resolve(pdfs); instead of just resolve();