How to return a formatted array of unique objects by value with underscore?

Question

Input:

var animals = [
    {category: "mammal", name: "dog", categoryID: "MAM"},
    {category: "fish", name: "pickerel", categoryID: "FIS"},
    {category: "mammal", name: "cat", categoryID: "MAM"},
    {category: "mammal", name: "monkey", categoryID: "MAM"},
    {category: "bird", name: "budgie", categoryID: "BIRD"}
];

Desired output:

var categories = [
 {name: "mammal", catId: "MAM"},
 {name: "bird", catId: "BIR"},
 {name: "fish", catId: "FIS"}
];

Is there a nice way to do it with underscore?

The closest I got was this jsFiddle:

var categories = _.groupBy(animals, function(animal) {
                    return animal.category;
                });

With this output:

Object {mammal: Array[3], fish: Array[1], bird: Array[1]}

But is there a way to return the desired output above in a nice way?

mu is too short · Accepted Answer · 2013-11-17 02:35:29Z

1

You can use reduce instead of groupBy to collect your names and IDs in a convenient format:

var collect_categories = function(o, e) {
    o[e.categoryID] = e.category;
    return o;
};
var o = _(animals).reduce(collect_categories, { })

and then a map to unpack that object into an array of objects:

var unpack = function(name, id) {
    return { name: name, catID: id };
};
var a = _(o).map(unpack);

The helper functions make more sense when you combine those with chain:

var categories = _(animals).chain()
                           .reduce(collect_categories, { })
                           .map(unpack)
                           .value();

I find that naming the functions makes the code less cluttered than anonymous functions and the names help to signal the code's intent.

Demo: http://jsfiddle.net/ambiguous/aS47C/

answered Nov 17, 2013 at 2:35

mu is too short

436k71 gold badges863 silver badges822 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to return a formatted array of unique objects by value with underscore?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related