Trying to get last x unique entries, and a corresponding value an another column via script

Question

So I'm trying to solve a problem with a sheet I have, it contains a Vlookup where people enter the date, their Intials, the custID and it displays a value from that row. (the original data is form responses, with emails, time stamps and 2 formulas working on the end)

This hasn't been the best solution so I was thinking about trying to automate this by showing the looked up value on the submission page, but this is quite beyond me.

So then I thought of perhaps an auto lookup via script that works as follows, (bearing in mind Col A is timestamp, B is email addy & column X has the value we want to return.)

I want it to start from last row, find the last x unique values from B, (possibly using A to find the greatest or last entry by date/time) and add row to an array for later (entire row isn't actually needed I guess, just B and X.)

Once it has it's 10 in the array, output Column B of array and Z of array)

Using my limited scripting knowledge and posts on here, this is where I'm at so far.

 function lastUniqueList(){ 
 var sheetName = "SheetNameHere"; // sheet name with data
 var columnNo = 2; // A = 1, B = 2 Column that we want the unqiue values from. IE last x unique email addresses.
 var uniqueToReturn = 10; //how many unique entries, ie, how many unique emails.
 var uniqueLookup = 24; // Column number that has the value we want looked up and returned.

 var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName);
 var data = sheet.getDataRange().getValues();
 var targetData = [];
 var counter = data.length;

while (targetData.length < uniqueToReturn)
  {



    if (data[counter][columnNo - 1] != "" && data[counter][columnNo - 1] != targetData.getDataRange.getValues()[columnNo - 1])
    {



      targetData.push(data.splice(counter, 1)[0]);
    }
    else
    {


      counter--;
    }
  }   



 }

So now I'm at a brick wall as to how to compare entries in my datarange to the array to avoid duplicates.

The 2nd part of the if statement, after the && isn't right. I'm trying to work it out.

If anyone could give me any pointers, or some good links, I'd appreciate it.

Also, I hope I've got it right and it's going backwards from last row. Logger did show correct row numbers etc when testing data.length

Will carry on searching the boards.

Answer 1

So here's what I came up with (assuming I understood the problem correctly):

function lastUniqueList(){ 
    var sheetName = "SheetNameHere"; // sheet name with data
    var columnNo = 2; // A = 1, B = 2 Column that we want the unqiue values from. IE last x unique email addresses.
    var uniqueToReturn = 10; //how many unique entries, ie, how many unique emails.
    var uniqueLookup = 24; // Column number that has the value we want looked up and returned.

    var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName);
    var data = sheet.getDataRange().getValues();
    var targetData = [];

    for (var counter=data.length-1; counter >= 0 && targetData.length < uniqueToReturn; counter--) {
        if (data[counter][columnNo - 1] == "") {
            continue;
        }
        if (targetData.some(function (element, index, array) {
            return data[counter][columnNo - 1] == element[columnNo - 1];
        })) {
            continue;
        }
        targetData.push(data[counter]);
    }
}

The secret sauce is in that Array.prototype.some method. It's asking if there are any elements in targetData that pass some test. The test is having a value at columnNo matching the one we're thinking of inserting. That's how we guarantee the unique values.

I also converted the while loop to a for loop because it's neater.

Here's the jsFiddle where I tested my solution.