Send a personnalised email from a Google Form - email

Question

I'm starting a new project. I have to send a confirmation email when someone purchases a book with my Google Form. By now, I can send an email when you complete the form but I can't put the name of the buyer and the number of books in the email. F.ex : Hello "John", you gonna receive your "3" books in a week.
I've tried something like this :
function sendEmail(e) {
var formreponse = e.responses;
var itemreponse = formreponse.getItemResponses();
var number= itemreponse[5].getResponse(); //because it's in the 5th columns of the spread sheets
var name= itemreponse[3].getResponse();
And then I just write a simple code like this
var TextToSend = "blablabla" + name + " blabla" + number + ".";
GmailApp.sendEmail(emailTo, subject, TextToSend, options);
But I've got an error message:
Cannot read property 'responses' of undefined.
And I don't know why!
It's very frustrating for me not to be able to finish this simple task.

Answer 1

Issues:
When running this function manually, through the editor, no event object is passed, and so e is undefined. You should not run this function manually.
responses is not a valid Event property of Form submit triggers.
Solution:
Install an onFormSubmit trigger, either manually or programmatically, so that the function will run automatically when the Form is submitted, and e will be populated.
Change e.responses to e.response:
var formreponse = e.response;
Reference:
Event Objects > Google Forms events > Form submit