如何使for循环脚本更有效？

Question

I'm very new to script writing in general, especially in GAS, and want to make sure I learn good habits. I wrote a for loop script that, in essence, does the following:

1. Read through column A starting at row 2
2. If cell above current cell in for loop is the same value, then clear the contents of the adjacent cell to the right of the current cell.

For example

Cell A1 contains "Something". Cell B1 contains "Exciting"

Cell A2 contains "New". Cell B2 contains "X"

Cell A3 contains "New". Cell B3 contains "Y"

Since A3 has the same value as cell A2 (that value being "New"), cell B3 (value currently "Y") is cleared so that there is no value in cell B3.

It seems to take a very long time to run, which I am sure is due to my novice writing, and I want to make this script as efficient as possible.

Do any of you scripting gods have any suggestions to make this script more efficient?

I would also appreciate any explanation as to why any suggestion would be more efficient for my own understanding, and so that anyone that happens to find this posting, later on, can understand it as well.

Here is the script:

function testCode() {
 var ss = SpreadsheetApp.getActiveSpreadsheet();
 var sheet = ss.getSheetByName("Test 1");
 var source = sheet.getRange("A2:A");

 for (i = 2; i < source.getLastRow(); i++) {
 var currentCell = sheet.getRange(i,1).getValue();
 var cellAbove = sheet.getRange(i-1,1).getValue();
 var cellRight = sheet.getRange(i,2);
 if (currentCell == cellAbove){
 cellRight.clearContent(),({contentsOnly:true});
  }
 }
}

THANK YOU

Answer 1

The biggest issue is that you are getting three new ranges in every loop. There is a way to do this without getting new ranges in the loop. You'll need to get the data in both columns A and B.

function testCode() {
  var cellAbove,currentCell,cellRight,data,lastRow,L,sheet,source,ss;

  ss = SpreadsheetApp.getActiveSpreadsheet();
  sheet = ss.getSheetByName("Test 1");
  lastRow = sheet.getLastRow();

  source = sheet.getRange(2,1,lastRow-1,2);//Get data starting in row 2 and column 1
  //Get the number of rows that are the lastRow minus the number of rows not included 
  //at the top - get 2 columns

  data = source.getValues();//Get a 2D array of values
  L = data.length;//Get the number of elements in the outer array- which is the number of
  //rows in the array

  for (var i = 0; i < L; i++) {

    if (i == 0) {continue;} //If this is the first loop there is no value above it to check

    currentCell = data[i][0];
    cellAbove = data[i-1][0];

    if (currentCell == cellAbove){
      cellRight = sheet.getRange(i+1,2);
      cellRight.clearContent(),({contentsOnly:true});
    }
  }
}