how can we sort a Complex Business Variable List by a specified field?

Question

Sort an Array of Objects in JavaScript

Now let’s look at sorting an array of objects. Let’s take an array of band objects:

const bands = [
  { genre: 'Rap', band: 'Migos', albums: 2},
  { genre: 'Pop', band: 'Coldplay', albums: 4},
  { genre: 'Rock', band: 'Breaking Benjamins', albums: 1}
];

We can use the following compare function to sort this array of objects according to genre:

function compare(a, b) {
  // Use toUpperCase() to ignore character casing
  const genreA = a.genre.toUpperCase();
  const genreB = b.genre.toUpperCase();

  let comparison = 0;
  if (genreA > genreB) {
    comparison = 1;
  } else if (genreA < genreB) {
    comparison = -1;
  }
  return comparison;
}

bands.sort(compare);

/* returns [
{ genre: 'Pop', band: 'Coldplay', albums: 4 },
{ genre: 'Rap', band: 'Migos', albums: 2 },
{ genre: 'Rock', band: 'Breaking Benjamins', albums: 1 }
] */

Answer 1

Business object lists in BPM are TWList objects, not JavaScript arrays: tw.local.orders.sort(...) does not exist on 8.5.x (recent BAW releases expose toArray() on lists). The portable way: copy to an array, sort, copy back:

// server-side script: sort tw.local.orders (list of Order) by total, descending, then by number
var arr = [];
for (var i = 0; i < tw.local.orders.listLength; i++) arr.push(tw.local.orders[i]);
arr.sort(function (a, b) {
  if (b.total !== a.total) return b.total - a.total;                       // numbers
  return (a.number || "").localeCompare(b.number || "");                   // strings
});
var sorted = new tw.object.listOf.Order();
for (var j = 0; j < arr.length; j++) sorted.insertIntoList(j, arr[j]);
tw.local.orders = sorted;

// generic helper: sortListBy(list, field, direction)
function sortListBy(list, field, desc) {
  var arr = []; for (var i = 0; i < list.listLength; i++) arr.push(list[i]);
  arr.sort(function (a, b) {
    var x = a[field], y = b[field];
    if (x instanceof Date || (x && x.getTime)) { x = x.getTime(); y = y.getTime(); }               // dates
    var r = (typeof x === "number" && typeof y === "number") ? x - y : String(x == null ? "" : x).localeCompare(String(y == null ? "" : y));
    return desc ? -r : r;
  });
  return arr;                       // caller copies back into a typed list (see below)
}

// simpler generic helper: sort in place by replacing the elements (keeps the list type)
function sortList(list, cmp) {
  var arr = []; for (var i = 0; i < list.listLength; i++) arr.push(list[i]);
  arr.sort(cmp);
  for (var j = 0; j < arr.length; j++) list[j] = arr[j];
}
sortList(tw.local.orders, function (a, b) { return new Date(b.created) - new Date(a.created); });   // newest first

Client side (coach): the bound list of a UI Toolkit table is a plain array with items on some releases - use var d = ${Table}.getData(); d.sort(cmp); ${Table}.setData(d);, or simply make the columns sortable and let the user click. Stable sorting: JavaScript's sort is stable in modern engines and in Rhino on BAW; on old Rhino add the index as a tiebreaker.

References

• JavaScript API - lists (listLength, insertIntoList)
• BPM UI Toolkit - Table sorting