Multiple OR conditions in time difference - date

Question

I want to make a script that send me mail whith the content of what I've enterd in a form some days after the form is submitted. As a help for students to study. In the form enter what to study, then 1 day, 7 days and 28 days later get that in a mail.
I've made a form that collect time, recipient adress, subject and body for the mail. These are saved in a Google spreadsheet.
The code kind of work. But it send all of the mail from my test input in the sheet. I've added one 6 days ago, one yesterday and one today.
Today I should only get one mail and tomorrow two. But I get all of them today.
I think it's this line:
if (diffDays == 1 || diffDays == 7 || diffDays == 28) continue;
I've trided to change it, searched other ways of writing it, as array for example.
Here's the full code:
function createTimeDrivenTriggers() {
ScriptApp.newTrigger('reminder')
.timeBased()
.everyDays(1)
.atHour(16) // Change time of day here
.inTimezone("Europe/Stockholm")
.create();
}
function reminder() {
var today = new Date(); // Today
var sheet = SpreadsheetApp.getActiveSheet();
var range = sheet.getDataRange();
var data = range.getValues();
var headerRows = 1;
for (i=0; i<data.length; i++){
if (i < headerRows) continue;
var row = data[i];
var time = row[0];
// Get time difference
var timeDiff = Math.abs(today.getTime() - time.getTime());
var diffDays = Math.ceil((timeDiff) / (1000 * 3600 * 24)-1);
if (diffDays == 1 || diffDays == 7 || diffDays == 28) continue;
var recipient = row[1];
var subject = row[2];
var body = row[3];
// Send mail
GmailApp.sendEmail(recipient, subject, body)
}
}
Thanks

Answer 1

Make sure to execute the code only when your if statement is true.
Include all code after if statement in the statement itself, only executing it when diffDays = 1, 2 or 28.
function reminder() {
var today = new Date(); // Today
var sheet = SpreadsheetApp.getActiveSheet();
var range = sheet.getDataRange();
var data = range.getValues();
var headerRows = 1;
for (i=0; i<data.length; i++){
if (i < headerRows) continue;
var row = data[i];
var time = row[0];
// Get time difference
var timeDiff = Math.abs(today.getTime() - time.getTime());
var diffDays = Math.ceil((timeDiff) / (1000 * 3600 * 24)-1);
if (diffDays == 1 || diffDays == 7 || diffDays == 28) {
var recipient = row[1];
var subject = row[2];
var body = row[3];
// Send mail
GmailApp.sendEmail(recipient, subject, body)
}
}
}

Answer 2

Note that continue means "stop processing this iteration of whatever loop is getting executed, and begin the next iteration." So your script sends reminders on every day except the days you want to remind them.
Changing your test to an "AND NOT", moving the code for reminding inside the existing check, or using a more expressive syntax like switch will satisfy your intent.
switch (diffDays) {
case 1:
case 7:
case 28:
sendReminder(your, Args, Here);
break;
case 0:
sendWelcome(some, other, Args);
break;
...
default:
break;
}
...
function sendReminder(your, Args, Here) {
/* Code that uses function arguments to build and send an email */
}
"And not" meaning if (diffDay != 1 && diffDay != ...), i.e. "if it's not this, and not that, and not this other thing, and not..."