NodeJS mailparser not being executed - node.js

Question

I am new to NodeJS. The following code snippet from my script is not executing nor it is logging any errors.
console.log('Process attachment');
const simpleParser = require('mailparser').simpleParser;
console.log('Process attachment');
simpleParser(data.Body, (err, mail) => {
if (err) {
console.log('attachment error');
console.log(err)
callback(null, null);
} else {
console.log('attachment success');
console.log(mail)
console.log(mail.attachments[0])
console.log(mail.attachments[0].content)
console.log(mail.attachments[0].content.toString('ascii'))
callback(null, null);
}
})
console.log('Exit');
process.exit();
Process attachment and Exit are being logged in the console but for some reason the code never goes in either the if or the else. So it looks like the simpleParser function is not being executed for some reason. data.Body contains a full email body. Is there anything obvious i am missing ? Thanks.

Answer 1

Why don't you use promises instead ?
This will work
simpleParser(data.Body).then(mail=>{
console.log('attachment success');
console.log(mail)
console.log(mail.attachments[0])
console.log(mail.attachments[0].content)
console.log(mail.attachments[0].content.toString('ascii'))
}).then(()=>{
console.log('Exit');
process.exit();
}).catch(err=>{
console.log('attachment error');
console.log(err);
})
And if you want to make it look simpler, cleaner use Async/Await like this
const parseMail = async ()=>{
try {
let mail = await simpleParser(data.Body);
console.log('attachment success');
console.log(mail)
console.log(mail.attachments[0])
console.log(mail.attachments[0].content)
console.log(mail.attachments[0].content.toString('ascii'))
}
catch(err) {
console.log('attachment error');
console.log(err);
}
console.log('Exit');
process.exit();
}

Answer 2

You are terminating the script prematurely.
simpleParser is being executed asynchronously. Therefore this bit console.log('Exit'); process.exit(); is being called before your simpleParser has finished.

Answer 3

We experienced this exact same behavior. The above responders are correct in that the console.log commands are not logging anything within the mailparser function because it is running asynchronously and the calling function is exiting without waiting on the mailparser to do its thing.
The simple solution for us was to just call the mailparser with await so the calling function waits on mailparser to complete before it continues.
So, instead of:
simpleParser(data.Body, (err, mail) => {console.log('message');});
Try this:
let mail = await simpleParser(data.Body);
if (mail != null) {console.log('message');};
For what it's worth, I think the asynchronous simpleParser function without the await should still be running through its internal code. It's just the logging messages won't be recorded as the calling function may have exited at the time.