Gathering all the unique values from one column and outputting them in another column..?

Question

I have this form of a spreadsheet:

 A   B   C  D
abc abc abc 1
def ghi jkl 1
mno pqr stu 3
vwx yza bcd 4
mno pqr stu 5
mno pqr stu 5
vwx yza bcd 5
mno pqr st         


        

Answer 1

Currently, in V8 engine, the easiest way to do this is to use Set:

/**
 * @returns {Object[]} Gets unique values in a 2D array
 * @param {Object[][]} array2d
 * @private
 */
const getUnique_ = array2d => [...new Set(array2d.flat())];

/**
 * Gets Values from a column, makes it unique and sets the modified values
 *   to the next column
 * @param {string} sheetName
 * @param {number} column Number of the column to uniquify
 * @param {number} headers Number of headers
 * @returns void
 */
const uniquifyAColumn = (sheetName = 'Sheet1', column = 3, headers = 1) => {
  const sh = SpreadsheetApp.getActive().getSheetByName(sheetName),
    rg = sh.getRange(1 + headers, column, sh.getLastRow() - headers, 1),
    values = rg.getValues(),
    uniqueValues = getUnique_(values).map(e => [e]);
  rg.offset(0, 1, uniqueValues.length).setValues(uniqueValues);
};