Google App Script : Get Content from Google Doc and Send Mail

function sendMail() {
//open document by URL
var doc = DocumentApp.openByUrl("");

//get content from Google document
var body = doc.getBody().getText();
// Get the email address of the active user — that’s you.
var email = Session.getActiveUser().getEmail();
// Get the name of the document to use as an email subject line.
var subject = “Inform to join event.”;
// Send yourself an email with a link to the document.
GmailApp.sendEmail(email, subject, body);