In Javascript, how can I Rename/Renumber a set of properties?

Question

This is one of those questions I'm ashamed to even ask, but I'm working with an external JSON source and I'm forced to do something ugly. So here goes...

I have 'dirty' Javascript object, with property names containing a number at their end:

{ "Friend1" : "Bob",
  "Friend6" : "Fred",
  "Friend632" : "Gonzo",
  "FriendFinder1" : "Dolly",
  "FriendFinder4294" : "Jan"
}

I'm trying to figure out a way to clean-up/"zero-index" these property names so the object would look like:

{ "Friend0" : "Bob",
  "Friend1" : "Fred",
  "Friend2" : "Gonzo",
  "FriendFinder0" : "Dolly",
  "FriendFinder1" : "Jan"
}

I'm referencing this indexOf/Regex code: Is there a version of JavaScript's String.indexOf() that allows for regular expressions?

Any strategies you could recommend for doing this? I'll post where I'm at in a bit. Many thanks!

why don't you use arrays? `{"Friends":["Bob","Fred","Gonzo"], "FriendFinders":["Dolly","Jan"]}` ? — olsn, Mar 28 '13 at 21:13

Francis Avila · Accepted Answer · 2013-03-28T22:03:52.147

Take the "base" of a key and append items with a common base to an array using the original index. (This produces a sparse array.) Then stretch it out again by enumerating each item with a common base into a new key with 'base'+enumeratedindex.

The trick here is to use a method like forEach to enumerate the array--this will only visit assigned items in a sparse array, allowing you to determine the sort order just by using the original index-part of the key.

If you don't have access to forEach, you can accomplish a similar task by including the key in the array items. Instead of an intermediate array like this:

{Friend: [undefined, "Bob", undefined, undefined, undefined, undefined, "Fred"]}

You have one like this:

{Friend: [[6, 'Fred'],[1, 'Bob']]}

Then you sort the array and visit each item in a foreach loop, extracting the second item.

Here is code:

function rekey(obj) {
    var rekey = /^(.*?)(\d+)$/;
    var nestedobj = {}, newobj = {};
    var key, basekeyrv, newkey, oldidx, newidx;
    function basekey(key) {
        return rekey.exec(key).splice(1);
    }
    for (key in obj) {
        if (obj.hasOwnProperty(key)) {
            basekeyrv = basekey(key);
            newkey = basekeyrv[0];
            oldidx = parseInt(basekeyrv[1], 10);
            if (!nestedobj[newkey]) {
                nestedobj[newkey] = [];
            }
            nestedobj[newkey][oldidx] = obj[key];
        }
    }
    for (key in nestedobj) {
        if (nestedobj.hasOwnProperty(key)) {
            newidx = 0;
            nestedobj[key].forEach(function(item){
                newobj[key+newidx++] = item;
            });
        }
    }
    return newobj;
}


rekey({
  "Friend1" : "Bob",
  "Friend6" : "Fred",
  "Friend632" : "Gonzo",
  "FriendFinder1" : "Dolly",
  "FriendFinder4294" : "Jan"
});

produces

{Friend0: "Bob",
 Friend1: "Fred",
 Friend2: "Gonzo",
 FriendFinder0: "Dolly",
 FriendFinder1: "Jan"}

Alternatively, without using forEach:

function rekey(obj) {
    var rekey = /^(.*?)(\d+)$/;
    var nestedobj = {}, newobj = {};
    var key, basekeyrv, newkey, oldidx, newidx;
    function basekey(key) {
        return rekey.exec(key).splice(1);
    }
    for (key in obj) {
        if (obj.hasOwnProperty(key)) {
            basekeyrv = basekey(key);
            newkey = basekeyrv[0];
            oldidx = parseInt(basekeyrv[1], 10);
            if (!nestedobj[newkey]) {
                nestedobj[newkey] = [];
            }
            nestedobj[newkey].push([oldidx, obj[key]]);
        }
    }
    for (key in nestedobj) {
        if (nestedobj.hasOwnProperty(key)) {
            nestedobj[key].sort();
            for (newidx = 0; newidx < nestedobj[key].length; newidx++) {
                newobj[key+newidx] = nestedobj[key][newidx][1];
            }
        }
    }
    return newobj;
}

Holy crap man- you've gone beyond any possible amount of help I ever thought I would get on this. Thank you so much! This will take me a bit to digest, but I can't thank you enough for this. Cheers! — Hairgami_Master, Mar 29 '13 at 14:25
Does this example disregard keys such as "Group" that don't have any number after them? I see your rekey regex targeting anycharactersequence+anynumbersequence but I can't quite grasp how it's being used. — Hairgami_Master, Mar 29 '13 at 14:37
This code will start spewing errors about null values if any key in your object doesn't match the regex. It's used in the `basekey` function, which must return `['name', 'sortint']` for a given key. — Francis Avila, Mar 29 '13 at 16:42
Many thanks- I added a check for valid regex sequence in the if(obj(has key) switch statement and it works perfectly. Again- thank you so much for doing this- I can't believe you did this for me. — Hairgami_Master, Mar 29 '13 at 18:40

score 0 · Answer 2 · answered Mar 28 '13 at 21:18

Could you try doing the following:

{
 friend: new Array(),
 friendFinder: new Array()
}

then you can:

friend.push() - Add to array

var index = friend.indexOf("Bob") - find in array

friend.splice(index, 1) - remove from the array at index the 1 is for the number to remove.

In Javascript, how can I Rename/Renumber a set of properties?

2 Answers2