Lodash - Find deep in array of object

Question

I have an array of an object like this

[
    {
        'a': 10,
        elements: [
            {
                'prop': 'foo',
                'val': 10
            },
            {
                'prop': 'bar',
                'val': 25
            },
            {
                'prop': 'test',
                'val': 51
            }
        ]
    },
    {
        'b': 50,
        elements: [
            {
                'prop': 'foo',
                'val': 30
            },
            {
                'prop': 'bar',
                'val': 15
            },
            {
                'prop': 'test',
                'val': 60
            }
        ]
    },
]

What I need is sum the property Val when prop is foo . So, I have to search through elements and get all objects where prop is foo . With this objects, I should sum the val property.

I tried to use many combinations of _.find , _.pick and so on, but I don't get the right result. Can someone help me?

Answer 1

Here's a solution that flattens the elements and then filters the result to get the required elements before summing the val property:

var result = _.chain(data)
    .map('elements')               // pluck all elements from data
    .flatten()                     // flatten the elements into a single array
    .filter({prop: 'foo'})         // exatract elements with a prop of 'foo'
    .sumBy('val')                  // sum all the val properties
    .value()

Chaining is a way of applying a sequence of operations to some data before returning a value. The above example uses explicit chaining but could be (maybe should be) written using implicit chaining:

var result = _(data)
    .map('elements')
    .flatten()
    .filter({prop: 'foo'})
    .sumBy('val');

Answer 2

I've created library that you can use: https://github.com/dominik791/obj-traverse

findAll() method should solve your problem. The first parameter is a root object, not array, so you should create it at first:

var rootObj = {
  name: 'rootObject',
  elements: [
    {
      'a': 10,
       elements: [ ... ]
    },
    {
       'b': 50,
       elements: [ ... ]
    }
  ]
};

Then use findAll() method:

var matchingObjects = findAll( rootObj, 'elements', { 'prop': 'foo' } );

matchingObjects variable stores all objects with prop equal to foo . And at the end calculate your sum:

var sum = 0;
matchingObjects.forEach(function(obj) {
  sum += obj.val;
});

Answer 3

Here's a one liner solution to this problem:

 const _ = require('lodash') let deepFind = (JSONArray, keyPath, keyValue) => _.find(JSONArray, _.matchesProperty(keyPath, keyValue)) let JSONArray = [{a:1, b:2, c:{d: "cd"}}, {a:3, b:4, c:{d: "ef"}}, {a:3, b:4, c:[{d: "ef"}]} ] console.log(deepFind(JSONArray, "cd", "cd")) // {a:1, b:2, c:{d: "cd"}} console.log(deepFind(JSONArray, "b", 4)) //{a:3, b:4, c:{d: "ef"}} console.log(deepFind(JSONArray, ['c', 'd'], "cd")) //{a:1, b:2, c:{d: "cd"}} console.log(deepFind(JSONArray, 'c[0].d' /* OR ['c', '0', 'd']*/, "ef")) //{a:1, b:2, c:{d: "cd"}}

Answer 4

Disclosure: I am the author of that library

---

You can use _.eachDeep method from deepdash:

let sum = 0;
_.eachDeep(obj, (value, key, parent) => {
  sum += (key == 'prop' && value == 'foo' && parent.val) || 0;
});

here is an example for your case

Answer 5

You can loop through the data and get the sum.Try this:

 var arr=[ { 'a': 10, elements: [ { 'prop': 'foo', 'val': 10 }, { 'prop': 'bar', 'val': 25 }, { 'prop': 'test', 'val': 51 } ] }, { 'b': 50, elements: [ { 'prop': 'foo', 'val': 30 }, { 'prop': 'bar', 'val': 15 }, { 'prop': 'test', 'val': 60 } ] } ]; var sum=0; for(x in arr){ for(i in arr[x]['elements']){ if(arr[x]['elements'][i]['prop'] == 'foo'){ sum=sum+arr[x]['elements'][i]['val']; } } } console.log(sum);

USING FILTER:

 var arr=[ { 'a': 10, elements: [ { 'prop': 'foo', 'val': 10 }, { 'prop': 'bar', 'val': 25 }, { 'prop': 'test', 'val': 51 } ] }, { 'b': 50, elements: [ { 'prop': 'foo', 'val': 30 }, { 'prop': 'bar', 'val': 15 }, { 'prop': 'test', 'val': 60 } ] } ]; var sum=0; arr.filter(function (person) { person['elements'].filter(function(data){ if (data.prop == "foo"){ sum=sum+data.val; } }); }); console.log(sum);

Answer 6

here the solution that worked for me if anyone needs it. but my case was a bit different, I needed to find an array that matches the id.

here a flow function which is not really nesesary but it does make the code easier to read

const flow = functions => data =>
    functions.reduce((value, func) => func(value), data);

   const arr = [
        {
            'a': 10,
            elements: [
                {
                    'prop': 'foo',
                    'val': 10
                },
                {
                    'prop': 'bar',
                    'val': 25
                },
                {
                    'prop': 'test',
                    'val': 51
                }
            ]
        },
        {
            'b': 50,
            elements: [
                {
                    'prop': 'foo',
                    'val': 30
                },
                {
                    'prop': 'bar',
                    'val': 15
                },
                {
                    'prop': 'test',
                    'val': 60
                }
            ]
        },
    ]

    const result= _.flow([
        data => _.map(data, 'elements'), // get all elements from the array 
        data => _.flatten(data), // create a singler array 
        data => _.find(data, { val: 65 }) // find the needed value in array 
        // you can keep on adding logic here depending on your need
    ])(arr); // the inital array 
    

if you dont want to use the flow function it can also be done like that I think I didnt test the code but it should work

const results = _.find(_.flatten(_.map(arr, 'elements')), { val: 65 });