Efficient way to move item in javascript array in a specific position

Question

I'm looking for a way to reorder an array in javascript moving elements to a specific position.

My array is:

[
    {
        "id": 105142,
        "parent": null,
        "created": "2015-03-20T17:21:33.013+01:00"
    },
    {
        "id": 105150,
        "parent": null,
        "created": "2015-03-20T19:02:09.079+01:00"
    },
    {
        "id": 105160,
        "parent": null,
        "created": "2015-03-20T22:15:06.543+01:00"
    },
    {
        "id": 105190,
        "parent": null,
        "created": "2015-03-21T19:39:19.441+01:00"
    },
    {
        "id": 105193,
        "parent": null,
        "created": "2015-03-22T01:42:00.974+01:00"
    },
    {
        "id": 105195,
        "parent": 105193,
        "created": "2015-03-22T11:05:20.033+01:00"
    },
    {
        "id": 105197,
        "parent": null,
        "created": "2015-03-22T11:06:15.241+01:00"
    },
    {
        "id": 105203,
        "parent": 105193,
        "created": "2015-03-22T22:22:48.833+01:00"
    }
]

I have to move items where parent !== null under their parent. The result so will be:

[
    {
        "id": 105142,
        "parent": null,
        "created": "2015-03-20T17:21:33.013+01:00"
    },
    {
        "id": 105160,
        "parent": 105142,
        "created": "2015-03-20T22:15:06.543+01:00"
    },
    {
        "id": 105150,
        "parent": null,
        "created": "2015-03-20T19:02:09.079+01:00"
    },
    {
        "id": 105190,
        "parent": null,
        "created": "2015-03-21T19:39:19.441+01:00"
    },
    {
        "id": 105193,
        "parent": null,
        "created": "2015-03-22T01:42:00.974+01:00"
    },
    {
        "id": 105195,
        "parent": 105193,
        "created": "2015-03-22T11:05:20.033+01:00"
    },
        {
        "id": 105203,
        "parent": 105193,
        "created": "2015-03-22T22:22:48.833+01:00"
    },
    {
        "id": 105197,
        "parent": null,
        "created": "2015-03-22T11:06:15.241+01:00"
    }
]

Is there any js library to move efficiently the items without a lot of recursions?

Why do you fear recursion?

Bergi
– Bergi

2015-03-27 09:16:42 +00:00
Commented Mar 27, 2015 at 9:16 — Bergi
– Bergi, Commented Mar 27, 2015 at 9:16

tsh · Accepted Answer · 2015-03-27 09:23:49Z

1

Use Array.prototype.sort should be a good idea. The only tricky thing is the key for comparing. Here, A child node should be greater than it's parent; A child and its parent should both greater or lesser than other nodes. So compare the keys by the keys of itself and its parents. The following code shows how to do that:

var re = {};
for (var i = 0, l = a.length; i < l; i++) re[a[i].id] = a[i];
var id = function (x) {
  var r = [x];
  for (; x; x = re[x].parent) {
    r.unshift(x);
  }
  return r.join('-');
};
a.sort(function (x, y) {
  if (x === y) return 0;
  if (id(x.id) > id(y.id)) return 1; else return -1;
});

Here, a is the array.

answered Mar 27, 2015 at 9:23

tsh

4,8386 gold badges32 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jordi Castilla · Accepted Answer · 2015-03-27 09:14:31Z

0

I think you don't need a library:

Ckeck arrays operations here and check splice()

The powerful splice() method lets you add and/or remove one or more elements from any point in an array:

You just have to find object, store it, remove from the array and insert in the new position.

answered Mar 27, 2015 at 9:14

Jordi Castilla

27.1k8 gold badges73 silver badges113 bronze badges

Comments

georg · Accepted Answer · 2015-03-27 09:23:32Z

0

No need for recursion, two nested loops will do:

data = [
    {
        "id": 105142,
        "parent": null,
        "created": "2015-03-20T17:21:33.013+01:00"
    },
    {
        "id": 105150,
        "parent": null,
        "created": "2015-03-20T19:02:09.079+01:00"
    },
    {
        "id": 105160,
        "parent": null,
        "created": "2015-03-20T22:15:06.543+01:00"
    },
    {
        "id": 105190,
        "parent": null,
        "created": "2015-03-21T19:39:19.441+01:00"
    },
    {
        "id": 105193,
        "parent": null,
        "created": "2015-03-22T01:42:00.974+01:00"
    },
    {
        "id": 105195,
        "parent": 105193,
        "created": "2015-03-22T11:05:20.033+01:00"
    },
    {
        "id": 105197,
        "parent": null,
        "created": "2015-03-22T11:06:15.241+01:00"
    },
    {
        "id": 105203,
        "parent": 105193,
        "created": "2015-03-22T22:22:48.833+01:00"
    }
]

result = [];

data.forEach(function(x) { 
    if(!x.parent) {
        result.push(x);
        data.forEach(function(y) {
            if(y.parent == x.id)
                result.push(y)
        })
    }
})

document.write("<pre>" + JSON.stringify(result,0,3));

This is "quadratic" in time, but will work fine unless you have millions of elements.

answered Mar 27, 2015 at 9:23

georg

216k57 gold badges324 silver badges401 bronze badges

1 Comment

Roberto Pezzali Over a year ago

I will have max 100 items in my array.

Collectives™ on Stack Overflow

Efficient way to move item in javascript array in a specific position

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related