Need a script to send an email if Cell Value Changes - google-apps-script

Question

Need Help to create a watchdog. I'm importing a webpage with some data. and want constantly check if imported data is the same whats my reference.
So I want the script to constantly compare 2 cells and if values became different, send me (the author) the email.
Want to compare H4 and E4
function sendEmails() {
var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Pricechecker");
var checkprice = sheet.getRange(E2:E2);
var currentprice = sheet.getRange(H4:H4);
if (currentprice <= checkprice) {
var emailAddress = "email#example.ge";
var message = "Discount";
var subject = "There is a Discount on your item";
MailApp.sendEmail(emailAddress, subject, message);
}
}

Answer 1

Solution:
You would need an Installable Trigger to automatically send email upon comparison of E4 and H4.
function createSpreadsheetEditTrigger() {
var ss = SpreadsheetApp.getActive();
ScriptApp.newTrigger('compare')
.forSpreadsheet(ss)
.onEdit()
.create();
}
function compare(e) {
if (e.range == "E4" || "H4") {
var sheet = SpreadsheetApp.getActiveSheet();
var checkPrice = sheet.getRange("E4").getValue();
var currentPrice = sheet.getRange("H4").getValue();
if (currentPrice <= checkPrice) {
var emailAddress = "email#example.ge";
var message = "Discount";
var subject = "There is a Discount on your item";
MailApp.sendEmail(emailAddress, subject, message);
}
}
}
Note that you only have to run createSpreadsheetEditTrigger() in Apps Script. The created trigger will run compare() everytime you make an edit to the spreadsheet. It will automatically check E4 and H4 and send email whether the condition is satisfied.
Console Output: