How do I reorder this array in Javascript based on another array?

Question

real_order = [ '1', '2', '3', '4'];

friends = [ { name: 'jess', id: '4'},
            { name: 'alex', id: '1'},
            { name: 'kat', id: '3' },
            { name: 'bob', id: '2' }
          ]

How do I make "friends" array "match" the elements in real_order? The result should be:

[ 
            { name: 'alex', id: '1'},
            { name: 'bob', id: '2' },
            { name: 'kat', id: '3' },
            { name: 'jess', id: '4'},
          ]

What is the most efficient solution?

Mikola · Accepted Answer · 2011-06-25 08:16:02Z

4

Here is some code that would do it:

var i, d = {}, result = [];
for(i=0; i<friends.length; ++i)
{
    d[friends[i].id] = friends[i];
}

for(i=0; i<real_order.length; ++i)
{
    result.push(d[real_order[i]]);
}

What this does is it creates a dictionary keyed on each of the friends' id, then uses the second array to do a look up and construct the new array. The resulting reordered array is stored in result.

answered Jun 25, 2011 at 8:16

Mikola

9,3542 gold badges36 silver badges42 bronze badges

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

1 Comment

Eineki Over a year ago

too quick, the very same solution I would had propose

KooiInc · Accepted Answer · 2011-06-25 11:26:33Z

4

Arrays can be sorted using your own custom sort algorithm, so you don't really need real_order. This is the way I'd do it (edit: added sort delegate for sorting descending):

var friends = [
           { id:4, name: 'jess'},
           { id:1, name: 'alex'},
           { id:3, name: 'kat' },
           { id:2, name: 'bob' }
];

var order = function(a,b,desc){
  return desc ? b.id - a.id : a.id - b.id;

},
orderDesc: function(a,b){return order(a,b,true);};

var friendsOrdered = friends.sort( order );
alert(friendsOrdered[0].name); //=> alex
alert(friendsOrdered[3].name); //=> jess

//or sort descending
var friendsOrdered = friends.sort( orderDesc );
alert(friendsOrdered[0].name); //=> jess
alert(friendsOrdered[3].name); //=> alex

edited Jun 25, 2011 at 11:26

answered Jun 25, 2011 at 11:05

KooiInc

124k32 gold badges145 silver badges181 bronze badges

Comments

dev-null-dweller · Accepted Answer · 2011-06-25 08:31:48Z

1

make sure that real_order is in global scope and this should do it:

friends.sort(function(a, b) {
    if (real_order.indexOf(a.id) > real_order.indexOf(b.id)) {
        return 1;
    }else{
        return -1;
    }
});

answered Jun 25, 2011 at 8:31

dev-null-dweller

29.5k3 gold badges68 silver badges87 bronze badges

Comments

Jan Turoň · Accepted Answer · 2011-06-25 10:56:06Z

0

One command solution. Ugly like jQuery, but people like John Resig love this style for some reason :)

friends.sort(
  (function(order){
     return function(a, b) {
       return order.indexOf(a.id)-order.indexOf(b.id);
     }
  })(real_order)
);

answered Jun 25, 2011 at 10:56

Jan Turoň

33.1k24 gold badges139 silver badges179 bronze badges

1 Comment

Jan Turoň Over a year ago

I am pretty sure this is most efficient in Javascript

Collectives™ on Stack Overflow

How do I reorder this array in Javascript based on another array?

4 Answers 4

1 Comment

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related