Sum elements of an array with specific attribute

Question

I wanna sum the elements of an array, but not all. Let's say that my array is:

var example = [
                   {"id": 1, "value": 50, "active": true}, 
                   {"id": 2, "value": 70, "active": false}, 
                   {"id": 3, "value": 45, "active": true}, 
                   {"id": 4, "value": 50, "active": false}
               ];

What I need to do is sum just the values of the elements with "active":true.

There's a way to do that? Maybe is too simple, but right now, my brain is dead.

I'm using Javascript and AngularJs.

Thanx in advance.

score 3 · Answer 1 · answered Aug 17 '19 at 01:16

3

You can use filter and reduce like so:

var a = [{"id": 1, "value": 50, "active": true}, {"id": 2, "value": 70, "active": false}, {"id": 3, "value": 45, "active": true}, {"id": 4, "value": 50, "active": false}]

var result = a.filter(o => o.active).reduce((acc, cur) => cur.value + acc, 0)

console.log(result)

answered Aug 17 '19 at 01:16

Asleepace

2,966
1
16
29

@ChuckVillavicencio glad to help! – Asleepace Aug 17 '19 at 01:45

score 1 · Answer 2 · answered Aug 17 '19 at 01:25

You can just use reduce, using the fact that in a numeric context true = 1 and false = 0:

var a = [{"id": 1, "value": 50, "active": true}, {"id": 2, "value": 70, "active": false}, {"id": 3, "value": 45, "active": true}, {"id": 4, "value": 50, "active": false}]

var result = a.reduce((a, c) => a + c.value * c.active, 0)

console.log(result)

Or if you prefer, using the ternary operator:

var a = [{"id": 1, "value": 50, "active": true}, {"id": 2, "value": 70, "active": false}, {"id": 3, "value": 45, "active": true}, {"id": 4, "value": 50, "active": false}]

var result = a.reduce((a, c) => a + (c.active ? c.value : 0), 0)

console.log(result)

Cool the fact of numeric value... didn't think about it – Chuck Villavicencio Aug 17 '19 at 01:38 — Chuck Villavicencio, Aug 17 '19 at 01:38

score 1 · Answer 3 · answered Aug 17 '19 at 01:30

1

You can prefer a simple syntax...

var example = [{"id": 1, "value": 50, "active": true}, {"id": 2, "value": 70, "active": false}, {"id": 3, "value": 45, "active": true}, {"id": 4, "value": 50, "active": false}];
var sum = 0

example.forEach(function(item, index){
  if (item["active"] == true) sum += item["value"];
});

console.log(sum);

answered Aug 17 '19 at 01:30

Gustavo Toro

420
4
9

1

Good! Neve thought to use forEach – Chuck Villavicencio Aug 17 '19 at 01:40

score 0 · Answer 4 · answered Aug 17 '19 at 05:19

I suggest you to use lodash If you need operation on array or collection

import lodash in file where you want to use it

import _ from 'lodash';
// or
const _ = require('lodash');

Apply filter and sumBy

var example = [
 {"id": 1, "value": 50, "active": true}, 
 {"id": 2, "value": 70, "active": false},
 {"id": 3, "value": 45, "active": true}, 
 {"id": 4, "value": 50, "active": false}
];
//Filter all active value
const filterData = _.filter(example, "active");
// const filterData = [
//  {"id": 1, "value": 50, "active": true}, 
//  {"id": 3, "value": 45, "active": true}, 
// ];

//Sum all value filter data
const sum = _.sumBy(filterData, "value");

console.log(sum)

Sum elements of an array with specific attribute

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