Google script to send conditional emails based on cells in google sheets - google-sheets

Question

I have a google sheet that I would like to have generate an email alert when one column is greater than the other. Specifically, column F > column G. Here is what I have so far, any advice would be greatly appreciated, as I do not have much skill writing functions.
function readCell() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName("Watch list");
var value = sheet.getRange("F2").getValue();
var value1 = sheet.getRange("G2").getValue();
if(value>value1) MailApp.sendEmail('example#gmail.com', 'subject', 'message');
};
Currently this only attempts to compare cell F2 to cell G2. Is there a way to make the function compare the entire F column against column G, and generate an email for each individual case where Fx > Gx ?
Thank you!!

Answer 1

You have to loop all over the range.
first instead of getting the content of one cell you'll need to get the content of all the column:
var value = sheet.getRange("F2").getValue();
become that
var values = sheet.getRange("F2:F").getValues();
(same for value1)
then you need to create an empty table that will collect the results:
var results = [];
and now you need to loop throught all the values:
for(var i=0;i<values.length;i++){
//do the comparaison and store result if greater for example
}
then you may send the result.
all put together it give something like that:
function readCell() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName("Watch list");
var values = sheet.getRange("F2:F").getValues();
var value1s = sheet.getRange("G2:G").getValues();
var results = [];
for(var i=0;i<values.length;i++){
if(values[i]<value1s[i]){
results.push("alert on line: "+(i+2)); // +2 because the loop start at zero and first line is the second one (F2)
}
}
MailApp.sendEmail('example#gmail.com', 'subject', results.join("\n"));
};
If you want to trigger that function automatically you'll also need to change the way you call the spreadsheet (instead of getActive.... you'll need to use openById)