Take HTML Input and Pass it from JavaScript to Email Using PHPMailer

In my basic code with JavaScript and PHP so far I can send an email with test data, the next step in the process is to add an attachment to the email .

Following this, the following doubts have arisen:

1. The first one related to the following code:

HTML

<input type="file" name="myFile" id="myFile" required/>

With this I take the attached file ready to send.

Now in my JavaScript, I have a function that successfully sends an email with test data:

function SendMail(){
    var cod="1234"; var subject="hello my friend";
    $.post("SendMail.php?cod="+cod+"&subject="+subject+""); // (1)
}

In (1) How do I take the value of that input, which is related to the file to send to be able to send it to my PHP file?

Something like

    $.get("SendMail.php?cod="+cod+"&subject="+subject+"&mail="ArchivoRelacionadoConElIDdelInput);

2. When you can send the file correctly, what is the appropriate way to format it to be added to the email to be sent?

Those are my doubts about it, I hope you can give me a hand. Your answers, as always, are welcome.

Thanks for your time.