javascript/jquery object inside object json data

Question

I have this data,

json:

var data = [{a:1,b:{amount: 10}, c:1},
            {a:2,b:{amount: 20}, c:1}, 
            {a:1,b:{amount: 30}, c:2}
           ];

and I want to do something like this:

SELECT SUM(b.amount) FROM data GROUP BY a, c

Javascript objects are not databases. Have you tried writing any code yet to implement the functionality you want? — CertainPerformance
– CertainPerformance, Commented Dec 5, 2018 at 1:31
i've tried using alaSQL.js but i just can't get the b.amount... — Jiel
– Jiel, Commented Dec 5, 2018 at 1:32

Joundill · Accepted Answer · 2018-12-05 01:59:12Z

2

You're trying to sum properties in an array of objects.

This will do it for you:

let sum = [];
data.forEach(function(el){
    if(sum[el.a] == undefined) sum[el.a] = []; 
    if(sum[el.a][el.c] == undefined) sum[el.a][el.c] = 0; 
    sum[el.a][el.c] += el.b.amount
});

You can then access the sum for a = 1, c = 2 with sum[1][2].

This code will work with larger data sets which require adding.

edited Dec 5, 2018 at 1:59

answered Dec 5, 2018 at 1:42

Joundill

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Joundill Over a year ago

Just multiply the amount by the quantity. Like this: sum[el.a][el.c] += el.b.amount * el.b.qty;

Joshua McClure · Accepted Answer · 2018-12-05 01:59:11Z

0

If I understand your questions correctly, you are asking how you can perform grouping and aggregation on a JSON object. As SQL can only be used in the realm of a database, you will need to use javascript functions such as forEach(), map(), filter(), reduce(), etc.

To make it easy on yourself, I recommend using a library like Lodash or Underscore.

Here is an example using Lodash:

let data = [
  {a:1, b:{amount: 10}, c:1},
  {a:2, b:{amount: 20}, c:1},
  {a:1, b:{amount: 30}, c:2}
];

let results = _.sumBy(data, 'b.amount');

console.log(results);

<script src="https://cdn.jsdelivr.net/npm/[email protected]/lodash.min.js"></script>

Using these libraries can take away a lot of the complexity of writing your own scripting, especially when dealing with nested objects and arrays.

I recommend using pure JS whenever possible and resort to libraries only when necessary.

answered Dec 5, 2018 at 1:59

Joshua McClure

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1 Comment

Jiel Over a year ago

ooh lodash, ya i've heard of it. i'll consider this also.. thank you

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