Converting from array to object in javascript

Question

I am facing a rather unusual problem using _.object(underscore library call). Below is my code :

var sortable =  [ [ 'c', 107 ],[ 'd', 59 ],[ 'e', 53 ],[ '5', 53 ],[ '6', 26 ],[ '3', 19 ],[ 'a', 10 ],[ '8', 7 ],[ '2', 5 ], [ '7', 4 ],[ '1', 3 ], [ '9', 3 ]];
         sortDict = _.object(sortable);

My output should be :

sortDict = { 'c':107 ,'d': 59,'e': 53 ,'5': 53,'6': 26,'3': 19,'a':10,'8': 7 ,'2':5, '7': 4,'1': 3, '9': 3 }

But what I am getting has me confused, see the output below :

sortDict = {'1': 3, '2':5, '3': 19, '5': 53, '6': 26, '7': 4, '8': 7 , '9': 3 , 'c':107 , 'd': 59, 'e': 53 , 'a':10 }

I am just trying to convert an array to an object here, but the order seems to have changed. Can you please help me achieve my desired output by any means.

There is no defined order to object keys in JavaScript objects, so your output is correct if the order is your only issue. — Andrew Whitaker, Jun 11 '14 at 12:42
but this is sorted array and i am trying to convert it to an object. — user3365783, Jun 11 '14 at 12:45
No such thing as sorted and object. The two are different paradigms. — Brad Christie, Jun 11 '14 at 12:46
http://stackoverflow.com/questions/1359761/sorting-a-javascript-object — Ram, Jun 11 '14 at 12:46
@user3365783: And it's been converted. Read what Andrew wrote. — cookie monster, Jun 11 '14 at 12:46
how do i achieve my desired output? That is what i am bothered about. — user3365783, Jun 11 '14 at 12:47
***YOU CAN'T***. If you maintain a separate Array and use that for the purpose of iteration, then do that. But then you might as well just use the original and not convert it. — cookie monster, Jun 11 '14 at 12:48
In javascript you can't. You'll never have a sorted object (sorted in the sense that the keys are in a specific order). — Brad Christie, Jun 11 '14 at 12:48
At this point I think you need to give a reason for your "goal". Sounds like an [XY Problem](http://meta.stackoverflow.com/questions/66377/what-is-the-xy-problem) to me. — cookie monster, Jun 11 '14 at 12:50
So why does that mean it needs to be ordered? Why does the recipient of the data require order from an unordered collection? — cookie monster, Jun 11 '14 at 12:51
but the spec according to which i go by, this is what it demands — user3365783, Jun 11 '14 at 12:53
my goal is to achieve my desired output thats all. i dont care how the user uses it, the spec demands it. — user3365783, Jun 11 '14 at 12:54
What spec? If it requires JSON, then it makes no sense that it requires the object to be sorted. — cookie monster, Jun 11 '14 at 12:54
_"i need to display an object in that order tats all.."_ Then use a sorted 2D array and iterate over the elements and treat them as key/value pairs. — Brad Christie, Jun 11 '14 at 12:55
If stackoverflow cant answer my question there is no point in me asking the question.@cookie monster spec for the software we develop, tats the spec. — user3365783, Jun 11 '14 at 12:58
If the spec doesn't make sense you could always ask for it to be corrected. And if you don't see the point of your own question here, you're welcome to delete it. — source.rar, Jun 11 '14 at 13:06

score 1 · Accepted Answer · answered Jun 11 '14 at 13:40

1

var sortable = [
    ['c', 107],
    ['d', 59],
    ['e', 53],
    ['5', 53],
    ['6', 26],
    ['3', 19],
    ['a', 10],
    ['8', 7],
    ['2', 5],
    ['7', 4],
    ['1', 3],
    ['9', 3]
];
var sorted = '';
sorted +='{';
for (var i = 0; i < sortable.length; i++) {
    sorted += "'"+sortable[i][0]+"': " +sortable[i][1]+",";
}
sorted +='}';
var obj = sorted;
alert(JSON.stringify(obj));
alert(sorted);

answered Jun 11 '14 at 13:40

Soni Kamal

20
2

this creates that format, but cant be called as an object. – user3365783 Jun 11 '14 at 14:04

score 0 · Answer 2 · answered Jun 11 '14 at 13:56

If you are required to send an actual JSON object in sorted order, you can do that, because you can always write the string version of it in a specific order (you have a sorted array, right?). (JSON fundamentally being a string representation of a Javascript object.) But the in-memory representation of that Javascript object has no order constraints and its elements will come back via for...in in the order determined by whatever Javascript engine processes it. Even Object.keys() doesn't guarantee an order, but it does give you something you can sort.

If the receiving end of your data also uses Javascript, specifying an ordered object is pointless because it won't iterate that way; if the receiving end is Java, C#, or C++, then its inability to handle the data in any supplied order is pretty much a weakness in the design of that code. There is no a priori reason an unordered object should be delivered in a specific order because that's the opposite of 'unordered' and indicates that the requirements were written by someone...well, not completely qualified. (In fact, the idea that the keys must be delivered in a certain order implies a certain dangerous dependency between leading and trailing keys, and that should make you uncomfortable with the design.)

Converting from array to object in javascript

2 Answers2