Concat in a for loop google app scripts javascript

I’m trying to filter in an array by data in another array using concat in a for loop. The elements of the following code are logging correctly, but the final array is logging an empty array.

function Shipments (){
  var app = SpreadsheetApp;
  var movementSS = app.getActiveSpreadsheet();
  var infoSheet = movementSS.getSheetByName("Update Info");
  var orderInfoSheet = movementSS.getSheetByName("Order Info");

  var targetSheet = movementSS.getSheetByName("Shipments");
  var ShipLogSS = app.openByUrl(URL).getSheetByName("Shipping Details");

  var ShipArr = ShipLogSS.getRange(3,1,ShipLogSS.getLastRow(),ShipLogSS.getLastColumn()).getValues().
    filter(function(item){if(item[1]!=""){return true}}).
    map(function(r){return [r[0],r[1],r[2],r[4],r[10],r[11],r[16],r[18],r[23]]});

  var supplierData = orderInfoSheet.getRange(3,6,orderInfoSheet.getLastRow(),1).getValues().
    filter(function(item){if(item[0]!=""){return true}});

  var supplierList = [];
  for (var i in supplierData) {
    var row = supplierData[i];
    var duplicate = false;
    for (var j in supplierList) {
      if (row.join() == supplierList[j].join()) {
        duplicate = true;
    if (!duplicate) {

  var supplierFilter = [];
  for(var i = 0; i < supplierList.length; i++){
    var shipments = ShipArr.filter(function(item){if(item[4]===supplierList[i][0]){return true}});



Any help would be greatly appreciated!

16 thoughts on “Concat in a for loop google app scripts javascript”

  1. You need to assign the result of concat onto the supplierFilter in order to see the changes in later iterations and in the outer scope.

    You can also return the comparison done inside the .filter callback immediately, instead of an if statement – it looks a bit cleaner.

    var supplierFilter = [];
    for (var i = 0; i < supplierList.length; i++) {
        var shipments = ShipArr.filter(function (item) { return item[4] === supplierList[i][0]; });
        supplierFilter = supplierFilter.concat(shipments);

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