SendGrid personalization when sending emails on N to N relationship - node.js

Question

I'm trying to implement an email price alerts system. In my situation, one email can have multiple price alerts, thus, conflicting with SendGrid when sending the alert as it receives the following error:
message: 'Each email address in the personalization block should be ' +
'unique between to, cc, and bcc. We found the first duplicate ' +
'instance of [xxxxxxx#gmail.com] in the personalizations.0.to ' +
'field.',
field: 'personalizations.0',
help: 'http://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/errors.html#message.recipient-errors'
I have not found anything that shows my use case. The best that I get is to send the same email to multiple different recipients such as: https://sendgrid.com/docs/for-developers/sending-email/personalizations/#sending-the-same-email-to-multiple-recipients
Is this something that can be achieved with SendGrid?!
My function:
function sendEmail (emailz, subject, body) {
const email = {
to: emailz,
from: 'salut#xxxxxxxxx.ro',
subject: subject,
text: body,
html: body
}
return sgMail.send(email)
.catch(error => {
console.error(error)
if (error.response) {
const {message, code, response} = error;
const {headers, body} = response;
console.error(body);
}
});
}
Actual email sending done:
try {
await sendEmail(
emailul,
'Alerta notificare pret!!!',
`Pretul produsului pe care il urmaresti este de ${pretulCurent} , sub alerta de pret setata de ${pretulDorit}. <br /> Produsul tau este: ${titlul} : ${link} `
)
} catch (e) {
await sendEmail('S-a produs o eroare', e.message)
throw e
}
Any help would be greatly appreciated. If this cannot be done using SendGrid, can you give me some pointers on other services where this situation might apply ?

Answer 1

Okay, if I understand you correctly, the problem here seems to be avoiding duplicates in your to email field. I suggest you check for duplicates before pushing to SendGrid (SendGrid won't do it for you) for each batch/job.
SendGrid accepts either an array of strings, or comma-delimited values, so you could try something like this:
var finalEmailul = [];
// for each email in the list, check - if it doesn't exist, push it in
if(finalEmailul.indexOf(emailul) < 0){
finalEmailul.push(emailul);
};
// then use 'finalEmailul' in your 'sendEmail' function
try {
await sendEmail(
finalEmailul, // <- use here. If you want it to be comma-delimited, use finalEmailul.join(",")
'Alerta notificare pret!!!',
`Pretul produsului pe care il urmaresti este de ${pretulCurent} , sub alerta de pret setata de ${pretulDorit}. <br /> Produsul tau este: ${titlul} : ${link} `
)
} catch (e) {
await sendEmail('S-a produs o eroare', e.message)
throw e
}