how to move an objects in the array after changing key

Question

I have an array with objects sorted by key 'order'

[
  {order: 1, id: 1, title: elem1},
  {order: 2, id: 2, title: elem2},
  {order: 3, id: 3, title: elem3},
  {order: 4, id: 4, title: elem4},
  {order: 5, id: 5, title: elem5}
]

after change key 'order' in 'elem2' to '4', array should look like this

[
  {order: 1, id: 1, title: elem1},  
  {order: 2, id: 3, title: elem3},
  {order: 3, id: 4, title: elem4},
  {order: 4, id: 2, title: elem2},
  {order: 5, id: 5, title: elem5}
]

I wanna move an objects in the array after changing key 'order' in some object in both direction

Possible duplicate of Sorting an array of JavaScript objects — VLAZ
– VLAZ, Commented Aug 10, 2016 at 20:25
@Vld - It's more an 'extract' and 'insert back' operation. Item #3 is moving as well. Not sure how this could be done with a sort. — Arnauld
– Arnauld, Commented Aug 10, 2016 at 22:03
@Arnauld By sorting-that's what sorting does, it arranges elements by default or specified rules. — Dave Newton
– Dave Newton, Commented Aug 10, 2016 at 22:14
@Arnauld seriously, dude? What sorting does is that it sorts stuff. objects.sort((a, b) => a.order - b.order). This complex and incomprehensible solution took me 5 seconds to implement. — VLAZ
– VLAZ, Commented Aug 11, 2016 at 9:29

madox2 · Accepted Answer · 2016-08-10 20:23:42Z

2

You can use Array.prototype.sort() function:

var elem1, elem2, elem3, elem4, elem5;
var arr = [
  {order: 1, id: 1, title: elem1},
  {order: 2, id: 2, title: elem2},
  {order: 3, id: 3, title: elem3},
  {order: 4, id: 4, title: elem4},
  {order: 5, id: 5, title: elem5}
];

arr[1].order = 4;
arr[3].order = 2;

arr.sort((a, b) => a.order > b.order);

answered Aug 10, 2016 at 20:23

madox2

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Comments

Arnauld · Accepted Answer · 2016-08-10 22:12:36Z

1

You can use .splice() to move the item and .forEach() to update the order property.

var arr = [
  {order: 1, id: 1, title: 'elem1'},
  {order: 2, id: 2, title: 'elem2'},
  {order: 3, id: 3, title: 'elem3'},
  {order: 4, id: 4, title: 'elem4'},
  {order: 5, id: 5, title: 'elem5'}
];

function moveItem(arr, from, to) {
  arr.splice(to - 1, 0, arr.splice(from - 1, 1)[0]);
  arr.forEach(function(e, i) { e.order = i + 1; });
}

moveItem(arr, 2, 4);

// formatted output
console.log(JSON.stringify(arr).split('},').join('},\n'));

edited Aug 10, 2016 at 22:12

answered Aug 10, 2016 at 21:44

Arnauld

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7 Comments

Dave Newton Over a year ago

Why wouldn't you just supply a sort function that compares the order property value of each element? I mean, your approach seems very brittle and unnecessary, no? And there's a working example from an hour ago.

Arnauld Over a year ago

@DaveNewton I may be missing something here, but I still don't get it. By just sorting (like the other answer does), item #3 will remain at the same position. This is not what the OP wants.

Dave Newton Over a year ago

In fairness to you it's not clear what the OP expects if two order values are the same.

Arnauld Over a year ago

@DaveNewton My understanding is that the OP wants to move element A at position B, shifting all elements between A and B towards the beginning of the array, then update the 'order' properties to reflect the new arrangement.

Arnauld Over a year ago

(or shifting towards the end of the array when B is before A)

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