ejs renderFile condition to check for null - node.js

Question

I have a mail route which is using ejs templates to choose different files. Now I want to check for different files and if the files does not exist or null it should choose default "en.ejs" file
inside ejs.renderFile I want to check for if(selectedLanguage !==null{}) but I am not sure how can I do it.
router.post('/mail', (req, res) => {
const subject = 'Test Mail';
const url = process.env.REPORT_URL;
const selectLanguage = req.body.selectedLang
sgMail.setApiKey(SGAPIKEY);
ejs.renderFile(__dirname + `/../ejs/reports/${selectLanguage}.ejs`, {
url: url
},
function (err, data) {
if (err) {
return err;
} else {
const msg = {
to: req.body.sendTo_email,
from: "test#test.com",
subject: subject,
html: data,
cc: req.body.cc,
attachments: [{
content: req.body.pdfBase64,
filename: 'file.pdf',
type: 'application/pdf',
disposition: 'attachment'
}]
};
sgMail.send(msg, error => {
if (error) {
return res.status(400).send({
sent: false
});
} else {
return res.status(200).send({
sent: true
});
}
});
}
});
});

Answer 1

You can check if the template file for the selected language exists (by using fs.access) and fallback to the en.ejs template before calling ejs.renderFile:
const fs = require('fs');
const getTemplateFileName = (lang, callback) => {
const defaultTemplate = __dirname + '/../ejs/reports/en.ejs';
const selectedLangTemplate = __dirname + `/../ejs/reports/${lang}.ejs`;
fs.access(selectedLangTemplate, fs.constants.F_OK, (err) => {
if (err) {
callback(defaultTemplate);
} else {
callback(selectedLangTemplate)
}
})
};
router.post('/mail', (req, res) => {
const subject = 'Test Mail';
const url = process.env.REPORT_URL;
const selectLanguage = req.body.selectedLang
sgMail.setApiKey(SGAPIKEY);
getTemplateFileName(selectLanguage, (filename) => {
ejs.renderFile(filename, { url }, function (err, data) {
if (err) {
return err;
} else {
const msg = {
to: req.body.sendTo_email,
from: "test#test.com",
subject: subject,
html: data,
cc: req.body.cc,
attachments: [{
content: req.body.pdfBase64,
filename: 'file.pdf',
type: 'application/pdf',
disposition: 'attachment'
}]
};
sgMail.send(msg, error => {
if (error) {
return res.status(400).send({
sent: false
});
} else {
return res.status(200).send({
sent: true
});
}
});
}
})
});
});