Question

I’m trying to take an array of many arrays that contain many objects and manipulate it into an array of objects.

So, let’s say I have an array that looks like this:

[
    [
        {Name: 'Josh', email: '[e-mail]', Points: 33},
        {Name: 'Doug', email: '[e-mail]', Points: 12}
    ],
    [
        {Name: 'Josh', email: '[e-mail]', Points: 11},
        {Name: 'Doug', email: '[e-mail]', Points: 18}
    ],
    [
        {Name: 'Josh', email: '[e-mail]', Points: 2},
        {Name: 'Doug', email: '[e-mail]', Points: 27}
    ]
]​

The Desired outcome would be an array of objects that has a ‘Points’ property to hold an array of the points. So it would look like this:

[
    {Name: 'Josh', email: '[e-mail]', Points: [33, 11, 2]},
    {Name: 'Doug', email: '[e-mail]', Points: [12, 18, 27]}
]

This problem seems simple, but I can’t seem to figure out the best way of doing this. If you want this data in a fiddle, I made this for you to play with: http://jsfiddle.net/Qhxzz/1/

Answer 1

Here’s one way using .reduce() and .forEach(). (You’ll need patches if you’re supporting older browsers.)

var consolidated = data.reduce(function(holder, arr) {
    arr.forEach(function(obj) {
        if (obj.email in holder.emails)
            holder.emails[obj.email].Points.push(obj.Points);
        else {
            holder.emails[obj.email] = obj;
            holder.result.push(obj);
            obj.Points = [obj.Points];
        }
    });
    return holder;
}, {emails:{},result:[]}).result;

---

And actually, we could flatten out the original Array using concat.apply(), and be left with one monolithic Array to iterate.

flat = [].concat.apply([], data);

This turns your data into this structure:

[{Name:"Josh", email:"[e-mail]", Points:33},
 {Name:"Doug", email:"[e-mail]", Points:12},
 {Name:"Josh", email:"[e-mail]", Points:11},
 {Name:"Doug", email:"[e-mail]", Points:18},
 {Name:"Josh", email:"[e-mail]", Points:2},
 {Name:"Doug", email:"[e-mail]", Points:27}]

And makes the consolidation a bit simpler by eliminating the need for the inner .forEach().

var consolidated = flat.reduce(function(holder, obj) {
    if (obj.email in holder.emails)
        holder.emails[obj.email].Points.push(obj.Points);
    else {
        holder.emails[obj.email] = obj;
        holder.result.push(obj);
        obj.Points = [obj.Points];
    }
    return holder;
}, {emails:{}, result:[]}).result;