how to build a string of id's from a json object

Question

My json object looks like:

User { ID: 234, name: 'john', ..);

I want to build a string of all the ID's.

How can I do this? is there a more elegant way than below?

var ids = '';
for(int x = 0; x < json.length; x++)
{
      ids += json[x].Id + ",";
}
// strip trailing id

Check out this question: stackoverflow.com/questions/759385/… — Gabe
– Gabe, Commented May 12, 2010 at 15:04
Your object is not valid JSON, not even valid JavaScript, and even if it was - it could only contain one single ID in its current form. So what does it really look like? — Tomalak
– Tomalak, Commented May 12, 2010 at 15:08

Tomalak · Accepted Answer · 2010-05-12 15:11:48Z

3

Assuming you an array of several users, which is what your question seems to imply (even though the example you show is neither valid JSON nor does it indicate that there is more than one object of type user)…

var jsonResult = [{ID: 1, name: 'John'}, {ID: 2, name: 'Bob'}];

var ids = jsonResult.map( function(user) {return user.ID;} ).join(',');
// ids will be "1,2"

answered May 12, 2010 at 15:11

Tomalak

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Comments

Nick Craver · Accepted Answer · 2010-05-12 15:04:41Z

2

You can make an array, use .push() to add items and .join() the result after, like this:

var ids = [];
for(int x = 0; x < json.length; x++)
{
      ids.push(json[x].Id);
}
var idString = ids.join(',');

answered May 12, 2010 at 15:04

Nick Craver

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Comments

Kamil Szot · Accepted Answer · 2010-05-12 15:11:39Z

0

For JavaScript 1.8 (ECMA-262 Edition 5) you might use Array.reduce to do basically the same thing:

[{id:1},{id:2},{id:3}].reduce(function(a,b) { return a+','+b.id }, '').substr(1)

If you prefer accumulating values in an array and concatenating them in the end do this:

[{id:1},{id:2},{id:3}].reduce(function(a,b) { a.push(b.id); return a }, []).join(',')

answered May 12, 2010 at 15:11

Kamil Szot

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