Google App Script Array Delete Duplicate Value From Top

I've got this working code that removes duplicates by comparing values in column B. If row 2 and 3 have the same values in column B then row 3 is deleted. function removeDuplicates

Solution 1:

I think this will do it.

  function removeDuplicates() {
  var ss=SpreadsheetApp.getActive();
  var sh=ss.getActiveSheet();
  var rg=sh.getDataRange();
  var row=rg.getRow();
  var col=rg.getColumn();
  var vA=rg.getValues();
  var nA=[];
  var duplicate=true;
  for(var i=0;i<vA.length;i++)
  {
    duplicate=false;
    for(var j=0;j<nA.length;j++)
    {
      if(vA[i][1]==nA[j][1])
      {
        duplicate=true;
        nA[j]=vA[i];
      }
    }
    if(!duplicate)
    {
      nA.push(vA[i]);
    }
  }
  rg.clearContent();
  sh.getRange(row, col, nA.length, nA[0].length).setValues(nA);
}

The outer loop is iterating through all of the rows of the active sheet and each time through it sets duplicate to false. The inner loop searches through nA[] looking for columnB matches if it finds one it sets duplicate to true. If duplicate is true then it doesn't get added to nA[]. The first time through nA.length is 0 so the inner loop doesn't do anything duplicate is false and so that element gets added to nA[]. It keeps doing this until there are no more rows and the rows that are in nA become the unique row. That's the way it use to run when I first did it. But since you wanted to keep the last duplicate instead of the first then I added nA[j]=vA[i]; which replaces the current element with the current match.

Just setup some fake data and play with it and you'll start to see how it works.