Change order of array of objects sorted by custom property

Question

I'm trying to write a script to change the order of an array of objects, ordered by an order property to let me move an element trough the array of objects I'm working on.

If I have:

[
  {order: 0, name: 'a'},
  {order: 1, name: 'b'},
  {order: 2, name: 'c'}
]

And I want to give to b the order 0, the result of the function will be:

[
  {order: 0, name: 'b'},
  {order: 1, name: 'a'},,
  {order: 2, name: 'c'}
]

Other examples:

// a to pos 2
input = [
  {order: 0, name: 'a'},
  {order: 1, name: 'b'},
  {order: 2, name: 'c'}
]

output = [
  {order: 2, name: 'a'},
  {order: 0, name: 'b'},
  {order: 1, name: 'c'}
]

// c to pos 1
input = [
  {order: 0, name: 'a'},
  {order: 1, name: 'b'},
  {order: 2, name: 'c'}
]

output = [
  {order: 0, name: 'a'},
  {order: 1, name: 'c'},
  {order: 2, name: 'b'}
]

This is my script so far:

var movedColumn         = { order: 4, name: 'd' };
var newIndex            = 1;
var oldIndex            = movedColumn.order;
var columns             = [ { order: 0, name: 'a' }, { order: 1, name: 'b' }, { order: 2, name: 'c' }, { order: 3, name: 'd' }, { order: 4, name: 'e' }, { order: 5, name: 'f' } ];

columns.sort(function asc(a, b) { return a.order - b.order; }).forEach(function(column) {
  if (column.order >= newIndex && column.order < oldIndex) {
    column.order += 1;
  }
});
columns.find(function(column) {
  return column.name === movedColumn.name;
}).order = newIndex;

http://codepen.io/FezVrasta/pen/XXgxWe?editors=001

It works well when I want to move b to order 0, but it doesn't work well if I want to move a to order 1.
I don't care about the order of the objects in the array, in my script I order them just to "pretty print" the result and for clarity.
What matters is the value of the order properties.

How can I fix it?

short version

I need to take an object and move it in the position defined by newIndex, shifting all the elements to prevent collisions (same order on two different objects)

This makes my head hurt, why would you move b up without changing the order, and what's it supposed to be sorted by ? — adeneo
– adeneo, Commented Jan 12, 2016 at 14:17
You're going to have to provide more examples of starting arrays and your desired results. It's not at all clear what you're trying to do. — Pointy
– Pointy, Commented Jan 12, 2016 at 14:17
@adeneo those objects will be rendered in the order defined by the order key, this is why I don't care about the order of them in the array but I care only about what order says. — Fez Vrasta
– Fez Vrasta, Commented Jan 12, 2016 at 14:20
I would recommend to use splice or do it manually with a for loop, and not use the sort method — Bergi
– Bergi, Commented Jan 12, 2016 at 14:28

Fez Vrasta · Accepted Answer · 2016-01-12 18:59:15Z

1

Probably this is a solution:

var movedColumn         = { order: 5, name: 'f' };
var newIndex            = 4;
var oldIndex            = movedColumn.order;
var columns             = [ { order: 0, name: 'a' }, { order: 1, name: 'b' }, { order: 2, name: 'c' }, { order: 3, name: 'd' }, { order: 4, name: 'e' }, { order: 5, name: 'f' } ];

columns.sort(function asc(a, b) { return a.order - b.order; }).forEach(function(column) {
  if (newIndex < oldIndex) {
    if (column.order >= newIndex && column.order < oldIndex) {
      column.order += 1;
    }
  }
  if (newIndex > oldIndex) {
    if (column.order > oldIndex && column.order <= newIndex) {
      column.order -= 1;
    }
  }
});
columns.find(function(column) {
  return column.name === movedColumn.name;
}).order = newIndex;

It seems to work in both the directions, it's not nice to see but it does the job.

Logically it will do nothing if you try to move the element to its very same order.

edited Jan 12, 2016 at 18:59

answered Jan 12, 2016 at 14:39

Fez Vrasta

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3 Comments

Bergi Over a year ago

Shouldn't that be column.order > oldIndex && column.order <= newIndex?

Fez Vrasta Over a year ago

It works in the way I've posted. You can try it here let me know if there's something wrong please.

Bergi Over a year ago

Yes, it really doesn't work when you move something upwards by more than 1 (example). Please test instead of only trying :-)

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