Unordered Dictionary in Javascript

Question

I would like to iterate through the key of an unordered dictionary in Javascript. I don't even know if it does exist or not.

At the moment I am having the following code :

var l = [5,3,2];
var unorderedDict = {};
for (var i=0; i<l.length; i++) {
    unorderedDict[l[i]] = 'foo';
}

My dictionary will then be like : {2:'foo', 3:'foo', 5:'foo'} or in my case, I would like to keep the ordering of the initial list (so : {5:'foo', 3:'foo', 2:'foo'})

How can I achieve this ?

Why do you want to keep the order in the object? BTW it is not possible. Is there any specific reason? — thefourtheye, May 10 '15 at 08:49
@user1058398 Nope, its not possible. Sounds like XY problem to me. What are you actually trying to do — thefourtheye, May 10 '15 at 08:50
Take a look at this one too http://stackoverflow.com/questions/5525795/does-javascript-guarantee-object-property-order — Ruslanas Balčiūnas, May 10 '15 at 08:55

Tushar · Accepted Answer · 2015-08-26T09:28:14.540

2

You cannot maintain order in object. If you want to maintain order use array:

var l = [5, 3, 2];
var val = ['foo', 'bar', 'baz'];
var unorderedDict = [];
//                  ^^
for (var i = 0; i < l.length; i++) {
  unorderedDict[l[i]] = val[i];
}

// Iterate over array:
for (var i = 0; i < unorderedDict.length; i++) {
  if (unorderedDict[i]) {
    console.log(unorderedDict[i]);
  }
}

EDIT

If you want the order to be the same as shown in l:

// Iterate over array:
for (var i=0; i<l.length; i++) {
    console.log(unorderedDict[l[i]]);
}

edited Aug 26 '15 at 09:28

answered May 10 '15 at 08:51

Tushar

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This is not correct. It will create new hash table. Order not preserved. I made a runnable snippet as edit and it proves that wrong. – Ruslanas Balčiūnas May 10 '15 at 09:04
@RuslanasBalčiūnas It does preserve order, since it is an `array` – Tushar May 10 '15 at 09:05
My bad, it is array with undefined missing values. But still this solution does not preserve order in `l`. You need a different data structure to accomplish that. – Ruslanas Balčiūnas May 10 '15 at 09:27
1

Or using the `l` to get the sequence – Tushar May 10 '15 at 09:30

Unordered Dictionary in Javascript

1 Answers1