Sending an Email from google sheets only once - google-apps-script

Question

The code below works perfectly and sends the email I need it to send on an "OnChange" trigger. However, it sends an email for EVERY checked box in row 7 which is overload, it just needs to send an email for newly checked boxes.
Any advice on how to add a condition in the below code for this?
function sendEmails() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName('Service');
var data = sheet.getDataRange().getValues();
for (var i = data.length - 1; i >= 1; i--) {
if (sheet.getRange(i,7).isChecked()){
var name = sheet.getRange(i,1).getValue();
var last = sheet.getRange(i,2).getValue();
var body = name + " " + last
var subject = 'New Service Item in Stock'
MailApp.sendEmail('me#mycompany.com', subject, body);
}
}
}
I haven't tried anything because there is nothing I could find online to get me in the right direction.
https://i.stack.imgur.com/cKfLv.png

Answer 1

Try unchecking them after you send them:
function sendEmails() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName('Service');
var data = sheet.getDataRange().getValues();
for (var i = data.length - 1; i >= 1; i--) {
if (sheet.getRange(i, 7).isChecked() && sheet.getRange(i,8).getValue() != "Sent") {
var name = sheet.getRange(i, 1).getValue();
var last = sheet.getRange(i, 2).getValue();
var body = name + " " + last
var subject = 'New Service Item in Stock'
MailApp.sendEmail('me#mycompany.com', subject, body);
sheet.getRange(i, 8).setValue("Sent");
}
}
}
Performance improvement:
function sendEmails() {
var ss = SpreadsheetApp.getActive();
var sh = ss.getSheetByName('Service');
var vs = sh.getRange(2, 1, sh.getLastRow() - 1, sh.getLastColumn()).getValues();
vs.forEach((r, i) => {
if (sh.getRange(i + 2, 7).isChecked() && r[7] == "Sent") {
let body = `${r[0]} ${r[1]}`;
let subject = "New Service Item in Stock";
MailApp.sendEmail('me#mycompany.com', subject, body);
sh.getRange(i, 8).setValue("Sent");
}
});
}