Google Script to remove duplicates from top to bottom - google-apps-script

Question

I have a script which combines three scripts to do the following:
1) Insert rows from one tab to the top of another tab
2) Remove duplicates from the tab in which the data was just added
3) Clear out the old tab from which the data was just ported over from
For the De-dupe script, it deletes rows starting at the bottom and then goes up. So I'm having established and existing data deleted. What I need it to do is start at the top and go down. So if new row records ported over from the first script are found to be a duplicate, it should delete those instead.
How can I get the de-dupe script to essentially process the opposite way?
I did find reverse logic with the below link, but I can't find a way to make it work with my script and keep getting errors. I'm also not sure if this would be the best methodology to fit in with my overall script.
Link: Removing Duplicate Rows in a google Spreadsheet from the end row
function Run(){
insert();
removeDuplicates();
clear1();
}
function insert() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var source = ss.getSheetByName('Candidate Refresh'); // change here
var des = ss.getSheetByName('Candidate Listing'); // change here
var sv = source
.getDataRange()
.getValues();
sv.shift();
des.insertRowsAfter(1, sv.length);
des.getRange(2, 1, sv.length, source.getLastColumn()).setValues(sv);
}
//Code in Question Start
function removeDuplicates() {
var sheet = SpreadsheetApp.getActiveSheet();
var rows = sheet.getLastRow();
var firstColumn = sheet.getRange(1, 2, rows, 1).getValues();
firstColumn = firstColumn.map(function (e) {return e[0]})
for (var i = rows; i >0; i--) {
if (firstColumn.indexOf(firstColumn[i-1]) != i-1) {
sheet.deleteRow(i);
}
}
}
//Code in Question End
function clear1() {
var sheet = SpreadsheetApp.getActive().getSheetByName('Candidate Refresh');
sheet.getRange('A2:K100').clearContent()
}
If new rows at the top of the sheet are found to be a duplicate, delete the new rows at the top.

Answer 1

try this:
function removeDuplicates() {
var sheet=SpreadsheetApp.getActiveSheet();
var rows=sheet.getLastRow();
var firstColumn=sheet.getRange(1, 2, rows, 1).getValues();
firstColumn = firstColumn.map(function(e){return e[0]})
var uA=[];
for (var i=rows;i>0;i--) {
if (uA.indexOf(firstColumn[i-1])!=-1) {
sheet.deleteRow(i);
}else{
uA.push(firstColumn[i-1]);
}
}
}