Google Spreadsheet script: Finds all similar texts in range (using difflib.js, percentage similarity)

find_similar.gs

/**
 * To use this script You must also add difflib module. 
 *     https://github.com/qiao/difflib.js
 * Add to project as difflib.gs minified version: 
 *     https://raw.githubusercontent.com/qiao/difflib.js/master/dist/difflib-browser.js
 */

function onOpen() {
  SpreadsheetApp.getUi().createAddonMenu()
    .addItem('Copy to new sheet', 'findSimilar')
    .addToUi();
}

function isSimilar(left, right, percent) {
  var ratio = new difflib.SequenceMatcher(null, String(left), String(right)).quickRatio();
  console.log(left + " " + right + " " + ratio);
  return ratio > percent;
}

function createNewSheet(name) {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  
  if (ss.getSheetByName(name) == null) {
    ss.insertSheet(name);
    return name;
  } else {
    return createNewSheet(name + "(0)");
  }
}  

function findSimilar() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();

  var activeSheet = SpreadsheetApp.getActiveSheet();
  var selectedRange = activeSheet.getActiveRange();

  var uniqueValues = new Array();

  var selectedCells = selectedRange.getValues();
  
  var percentage = 0.7
  
  for (var i = 0; i < selectedCells.length; ++i){
    var row = selectedCells[i];
    var firstValue = row[0];
    var duplicate = false;
    for (var j = 0; j < uniqueValues.length; ++j){
      if (isSimilar(firstValue, uniqueValues[j], percentage)) {
         duplicate = true;
         break;
      }
    }

    if (!duplicate){
      selectedRange.getCell(i + 1, 1).setBackground("red");
      uniqueValues.push(firstValue);
    }
  }
}