Summarize object properties in an array of objects into a single Lodash object

Question

I am trying to get it right and I am having problems, so I have to ask ppl with a lot of experience. I have an array of objects that let you call the elements to be called, and I need to bring some properties to the various objects in the array and sum them at the end. The user can make several choices, and I only need to summarize only the selected properties in the array that they gave me, so I thought maybe I could use the _.pick function in lodash. If possible, I would like to do this in a single loop, since an array of elements can have up to 1000 elements. Here is an example:

var items = [
{'lightBlue':4, 'darkBlue':2, 'red':4, 'orange':6, 'purple':7},
{'lightBlue':6, 'darkBlue':5, 'red':1, 'orange':2, 'purple':3},
{'lightBlue':2, 'darkBlue':4, 'red':3, 'orange':4, 'purple':9}
]

var userSelectedColors = ['lightBlue', 'darkBlue'];

What I want to see is all blue, like:

var summedUp = [{'lightBlue':12, 'darkBlue':11}];

Then summarize the results to get the total number no

var totalCount = 23

lodash. userSelectedColors 1 .

, !

Answer 1

_.sumBy

var totalCount = _.sumBy(userSelectedColors, _.partial(_.sumBy, items));

var items = [
  { 'lightBlue': 4, 'darkBlue': 2, 'red': 4, 'orange': 6, 'purple': 7 },
  { 'lightBlue': 6, 'darkBlue': 5, 'red': 1, 'orange': 2, 'purple': 3 },
  { 'lightBlue': 2, 'darkBlue': 4, 'red': 3, 'orange': 4, 'purple': 9 }
], userSelectedColors = ['lightBlue', 'darkBlue'];

var totalCount = _.sumBy(userSelectedColors, _.partial(_.sumBy, items));

console.log(totalCount);

<script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script>

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, :

var totalCount = _.sumBy(userSelectedColors, function(prop) {
    return _.sumBy(items, prop);
});

---

Lodash :

var totalCount = items.reduce(function(total, obj) {
    return total + userSelectedColors.reduce(function(total, prop) {
        return total + obj[prop];
    }, 0);
}, 0);

var items = [
  { 'lightBlue': 4, 'darkBlue': 2, 'red': 4, 'orange': 6, 'purple': 7 },
  { 'lightBlue': 6, 'darkBlue': 5, 'red': 1, 'orange': 2, 'purple': 3 },
  { 'lightBlue': 2, 'darkBlue': 4, 'red': 3, 'orange': 4, 'purple': 9 }
], userSelectedColors = ['lightBlue', 'darkBlue'];

var totalCount = items.reduce(function(total, obj) {
    return total + userSelectedColors.reduce(function(total, prop) {
        return total + obj[prop];
    }, 0);
}, 0);

console.log(totalCount);

<script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script>

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Answer 2

, , , , , , , @4castle. ( , 1000 .)

var items = [
    {'lightBlue':4, 'darkBlue':2, 'red':4, 'orange':6, 'purple':7},
    {'lightBlue':6, 'darkBlue':5, 'red':1, 'orange':2, 'purple':3},
    {'lightBlue':2, 'darkBlue':4, 'red':3, 'orange':4, 'purple':9}
]

var userSelectedColors = ['lightBlue', 'darkBlue'];

var sums = {};

_.each(items, function (item) {
    _.each(userSelectedColors, function (color) {
        sums[color] = (sums[color] || 0) + item[color];
    });
});

console.log('Summary: ', sums);

console.log('Grand total: ', _.sum(_.values(sums)));

:

Summary:  { lightBlue: 12, darkBlue: 11 }
Grand total:  23