CODEWITHSUNDEEP
javascriptarrayslodash
Filip Blaauw
Filip Blaauw

Reputation: 761

Get unique values, sum and count from an array using lodash

I have an array where I would like to get the unique values and the number of their occurrences, and sum the matching company names. I'm using lodash, and so far I'm able to get each unique value.

How can i efficiently get the number of each occurrence, and sum them? Price data is strings.

var data = [
 {"cat":"IT","company":"Apple", "price":"100.5"},
 {"cat":"IT","company":"Apple", "price":"100"},
 {"cat":"IT","company":"Google", "price": "100"},
 {"cat":"IT","company":"Apple", "price": "100"}
];

Result I need:

Company | Count | Sum
Apple   |   3   | 300.5
Google  |   1   | 100

My code so far:

var result = _.map(_.uniqBy(data, 'company'), function (item) {
  $('table').append('<tr><td>'+item.company+'</td></tr>');
});

Is it possible to do sum and count inside the same _.map function?

Upvotes: 3

Views: 4182

Answers (2)

RomanPerekhrest
RomanPerekhrest

Reputation: 92854

Pure JS(Ecmascript5) solution using Array.prototype.reduce() and Object.keys() functions:

var data = [
 {"cat":"IT","company":"Apple", "price":"100.5"},
 {"cat":"IT","company":"Apple", "price":"100"},
 {"cat":"IT","company":"Google", "price": "100"},
 {"cat":"IT","company":"Apple", "price": "100"}
], rows = "";

var result = data.reduce(function(r, o) {
    if (r[o.company]){
        ++r[o.company].count;
        r[o.company].price += Number(o.price);
    } else {
        r[o.company] = {count: 1, price: Number(o.price)};
    }
    return r;
}, {});

Object.keys(result).forEach(function(name){
  rows += '<tr><td>'+ name +'</td>' + 
          '<td>'+ result[name].count +'</td>' +
          '<td>'+ result[name].price +'</td></tr>';

});
$('table').append(rows);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
  <tr>
    <th>Company</th>
    <th>Count</th>
    <th>Sum</th>
  </tr>        
</table>

Upvotes: 5

Nenad Vracar
Nenad Vracar

Reputation: 122047

You can first groupBy company and then map and reduce to return array of objects for each company.

var data = [
 {"cat":"IT","company":"Apple", "price":"100.5"},
 {"cat":"IT","company":"Apple", "price":"100"},
 {"cat":"IT","company":"Google", "price": "100"},
 {"cat":"IT","company":"Apple", "price": "100"}
];

var group = _.groupBy(data, 'company')

var result = _.map(_.keys(group), function(e) {
  return _.reduce(group[e], function(r, o) {
    return r.count += +o.price, r
  }, {Company: e, count: 0, sum: group[e].length})
})

console.log(result)
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.15.0/lodash.min.js"></script>

Upvotes: 2

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