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?

Answer 1

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.