Loop script to copy and paste data, how to optimise - google-apps-script

Question

I got a sheet with data automatically refreshed everyday. Here is the structure:
data1 data2 data3 data4 data5 etc...
a1 a2 a3 a4 a5 etc...
b1 b2 b3 b4 b5 etc...
c1 c2 c3 c4 c5 etc...
I wrote a script to save these data in another sheet everyday. here is my script :
function savedata() {
var sheet = SpreadsheetApp.openById('my_id').getSheetByName('Sheet1');
var numRows = sheet.getLastRow()-1;
for(var i = 0; i < numRows; i++) {
var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet2")
var ss = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1")
var data1 = sheet.getRange('Sheet1!A2:G2').getValues();
sheet.appendRow(data1[0]);
ss.deleteRow(2)
}
}
As you can understand I'm looping through all my row copying them and deleting them one by one until there nothing left. Everything is added to a second sheet.
Is there a more effective way to do this job ?

Answer 1

Indeed we can optimize this code.
Few points to keep in mind:
Always try to use inbuilt appscript functions first instead of looping as looping consumes more time than inbuilt functions on server side and ultimately your script will be slow when data becomes huge.
Also, in your for loop, you have written SpreadsheetApp.getActiveSpreadsheet(). It will get the spreadsheet every time the loop runs, you dont have to do that, declare them outside of the loop and still you will get the same result. Unless your data is getting modified runtime, you dont want to do that.
Also, I don't think your data1 variable is fetching new range for new iteration of for loop, I think it brings the same row values and you will write same data in multiple rows in your destination sheet.
Now, you can code something like this to get the similar result in efficient way:
var sheet1 = SpreadsheetApp.openById("ID1").getSheetByName("Sheet1");
var sheet2 = SpreadsheetApp.openById("ID2").getSheetByName("Sheet2");
var content = sheet1.getRange(1, 1, sheet1.getLastRow(), sheet1.getLastColumn()).getValues(); //Get all the values starting from 1st row 1st column and till end of rows and columns
sheet2.getRange(1, 1,sheet1.getLastRow(), sheet1.getLastColumn()).setValues(content); //Get the same length and width to paste the data
sheet1.clear(); //You can put a condition here to make sure that all the data is copied successfully by checking if no. of rows in sheet1 and sheet2 is same
Also, there is difference between sheet1.clear() and sheet1.deleteRow(). If you use clear, it will just make the spreadsheet cells blank. If you use delete, it will delete the rows entirely and if you have only 5 rows, then after deletion, it will show you warning that you can't delete all the cells.
One more thing, delete fully blank rows and columns if you have no use of those as there is limit of 20 million cells in spreadsheets which includes cells in all the tabs.
EDIT
if(sheet2.getRange(1, 1).getValue().trim() == "")
{
var startIndex = 0; //I'm assuming your destination sheet is blank in first iteration
}
else
var startIndex = sheet2.getLastRow();
sheet2.getRange(startIndex+1, 1,sheet1.getLastRow(), sheet1.getLastColumn()).setValues(content);
Also one more important thing which I just added, see that I used .trim() in the if statement. The reason is, lets say you have entered 4-5 blank spaces by pressing spacebar in the A1 cell of destination sheet, then it will be considered as written row and getLastRow() will return 1 instead of any error. So, trim() here will remove all the white spaces of the A1 cell and check if it is still blank. It is very useful when you're checking for blank cells or values so that no once can bypass the code.