Is there a way to speed up this for loop in Google Script? - for-loop

Question

I have a for loop which is working on my google sheet but it takes around 5 minutes to filter through the 2100 rows of data. I have read about using filters and getting rid of the for loop all together but I'm fairly new to coding in Google Script and haven't been able to get my head around the syntax for this. Any advice greatly appreciated.
Code below:
function Inspect() {a
var sSheet = SpreadsheetApp.getActiveSpreadsheet();
var srcSheet = sSheet.getSheetByName("Inventory");
var tarSheet = sSheet.getSheetByName("Inspections");
var lastRow = srcSheet.getLastRow();
for (var i = 2; i <= lastRow; i++) {
var cell = srcSheet.getRange("A" + i);
var val = cell.getValue();
if (val == true) {
var srcRange = srcSheet.getRange("B" + i + ":I" + i);
var clrRange = srcSheet.getRange("A" + i);
var tarRow = tarSheet.getLastRow();
tarSheet.insertRowAfter(tarRow);
var tarRange = tarSheet.getRange("A" + (tarRow+1) + ":H" + (tarRow+1));
var now = new Date();
var timeRange = tarSheet.getRange("I"+(tarRow+1));
timeRange.setValue(now);
srcRange.copyTo(tarRange);
clrRange.clear();
//tarRange.activate();
timeRange.offset(0, 1).activate();
}
}
};

Answer 1

Yes, to speed-up you will need to get all the values first and apply your logic to the obtained 2D-arrays instead of cells, at the end you will use setValues to update your sheet. I would go for something like this:
function Inspect() {
var sSheet = SpreadsheetApp.getActiveSpreadsheet();
var srcSheet = sSheet.getSheetByName("Inventory");
var tarSheet = sSheet.getSheetByName("Inspections");
var srcLastRow = srcSheet.getLastRow();
var tarLastRow = tarSheet.getLastRow();
var srcArray = srcSheet.getRange(1,1,srcLastRow,9).getValues();//(A1:I(lastrow))
var tarArray = tarSheet.getRange(1,1,tarLastRow,9).getValues();//(A1:I(lastrow))
for (var i = 1; i < srcArray.length; i++) {
var val = srcArray[i][0];
if (val == true) {
var copyValues = srcArray[i].slice(1);//Get all elements from the row excluding first column (srcSheet.getRange("B" + i + ":I" + i);)
var now = new Date();
copyValues[8]=now;//set the time on column 9 (array starts at position 0!)
var tarNewLine = copyValues;
tarArray.push(tarNewLine);
//clear values on source (except column A):
for(var j=1;j<srcArray[i].length;j++){
srcArray[i][j]="";
}
}
}
tarSheet.clear();
tarSheet.getRange(1, 1,tarArray.length,tarArray[0].length).setValues(tarArray);
srcSheet.clear();
srcSheet.getRange(1, 1,srcArray.length,srcArray[0].length).setValues(srcArray);
};

Answer 2

You cannot get around a loop, but you should reduce the number of calls to the SpreadsheetApp to a minimum, see Apps Script Best Practices
It is not the for loop, but those calls that make your code slow. Instead, work with arrays as much as you can. Loops become of a problem if they are nested - this is also something you should avoid.
Sample how to perform most calls to SpreadsheetApp outside of the loop and work with arrays:
function Inspect() {
var sSheet = SpreadsheetApp.getActiveSpreadsheet();
var srcSheet = sSheet.getSheetByName("Inventory");
var tarSheet = sSheet.getSheetByName("Inspections");
var lastRow = srcSheet.getLastRow();
var Acolumn = srcSheet.getRange("A2:A" + lastRow);
var Avalues = Acolumn.getValues();
var srcRange = srcSheet.getRange("B2:I" + lastRow);
var srcValues = srcRange.getValues();
var array = [];
var now = new Date();
for (var i = 0; i < lastRow-1; i++) {
var val = Avalues[i][0];
if (val == true) {
srcValues[i].push(now);
array.push(srcValues[i]);
var clrRange = Acolumn.getCell(i+1, 1);
clrRange.clear();
}
}
var tarRow = tarSheet.getLastRow();
tarSheet.insertRowAfter(tarRow);
if(array.length!=0){
var tarRange = tarSheet.getRange("A" + (tarRow+1) + ":I" + (tarRow + array.length));
tarRange.setValues(array);
}
};