Is there a way I can make my script more efficient? - performance

Question

I have created the below script to add a timestamp when a cell equals a specific value. This script repeats for each row but it is not efficient. How can I make this simpler and quicker? Below is an extract of the script, it repeats for each row
function MyFunction() {
var ss = SpreadsheetApp.getActiveSpreadsheet()
var sheet = ss.getSheetByName('Overview')
var cell = sheet.getRange('H3').getValue()
var sent = sheet.getRange('p3').getValue()
if (cell == "Full" && sent == "") {
sheet.getRange('p3').setValue(new Date())
}
else if (cell == "Open" && sent == "") {
sheet.getRange('p3').setValue("")
}
}

Answer 1

Try this.
function MyFunction() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName('Overview');
// get range H3:P were H=8, P=16, 9 columns total or index 0 to 8
var data = sheet.getRange(3,8,sheet.getLastRow()-2,9).getValues(); // get range H3:P
var i = 0;
var row = null;
for( i=0; i<data.length; i++ ) {
row = data[i];
if( ( row[0] === "Full" ) && ( row[8] === "" ) ) {
row[8] = new Date();
}
// Your else doesn't do anything if blank set blank ??
row.splice(0,8); // extract only column P
}
sheet.getRange(3,16,data.length,1).setValues(data);
}

Answer 2

Try using setvalues() method of class range
function MyFunction() {
const ss = SpreadsheetApp.getActive()
const sh = ss.getSheetByName('Overview');
const rg = sh.getDataRange();
const vs = rg.getValues();
let vo = vs.map(r => {
if( r[7] == "Full") r[15]=new Date()
if( r[7] == "Open") r[15]='';
return [r[15]];
});
sh.getRange(2,16,vo.length,1).setValues(vo);
}