group objects array underscore js

Question

I'm getting an array back from an URL which looks like this:

[
   {
     id : 1,
     product_id : 101,
     price_new : 80,
     price_old : 90
   },
   {
     id : 2,
     product_id : 101,
     price_new : 80,
     price_old : 90
   },
   {
     id : 3,
     product_id : 102,
     price_new : 80,
     price_old : 90
   },
]

I would like to transform this, to:

[
   {
     product_id : 101,
     offers : [
     {
       id: 1
       price_new : 80,
       price_old : 90
     },{
       id: 2
       price_new : 80,
       price_old : 90
     }]
   },
   {
     product_id : 102,
     offers: [{
       id : 3,
       price_new : 80,
       price_old : 90
     }]
   },
]

Anyone who knows how to get this done using underscore js? Would love to get a solution using underscore cause we're using it in our entire project and it looks more clean, so...

Answer 1

You should be able to use underscore's groupBy method to group them, although it won't (on its own) remove the product_id from each record. You can then take each key and use them as array elements.

 var data = [{ id: 1, product_id: 101, price_new: 100, price_old: 90 }, { id: 2, product_id: 101, price_new: 100, price_old: 90 }, { id: 3, product_id: 102, price_new: 100, price_old: 90 }, ]; var grouped = _.chain(data).groupBy("product_id").map(function(offers, product_id) { // Optionally remove product_id from each record var cleanOffers = _.map(offers, function(it) { return _.omit(it, "product_id"); }); return { product_id: product_id, offers: cleanOffers }; }).value(); document.getElementById("results").textContent = JSON.stringify(grouped); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.7.0/underscore-min.js"></script> <pre id="results"></pre>