How to add values from a JSON array with unique parameter

Question

I am trying to create a map with unique key elements from an JSON array and set the value to the khey with a total of item property, qty for each objects with the same id. There are total 5 objects in the array. The objects with id: equals to 123 should add up to 40 and objects with id: equals 456 should add up to 90 but instead id:456 adds up to 130.

I have put together a fiddle for reference https://jsfiddle.net/5jdhatq2/2/

And here is the code

   id: 123,
   qty: 20
 },
 {
   id: 456,
   qty: 30
 },
 {
   id: 123,
   qty: 20
 },
 {
   id: 456,
   qty: 30
 },
 {
   id: 456,
   qty: 30
 }
]

var priceMap = new Map();
var dataArray = [123, 456];
var qty = 0;
for (var i = 0; i < dataArray.length; i++) {
 for (var j = 0; j < data.length; j++) {
   if (dataArray[i] == data[j].id) {
     var qty = qty + data[j].qty;
     priceMap.set(dataArray[i], qty);
   }
 }
}

console.log(priceMap.get(123), priceMap.get(456))
//expected outcome -- priceMap.get(123) -> 40 and priceMap.get(456) -> 90

Cant figure out what I am doing wrong here

Stark Jeon · Accepted Answer · 2020-08-09 02:28:05Z

2

TLDR

You need to clear qty after one loop

Answer

When execute first loop for (var i = 0; i < dataArray.length; i++)
qty is being accumulate ex-qty, I mean 40 (id=123), so you need clear qty cuz it is global variable

var data = [{
    id: 123,
    qty: 20
  },
  {
    id: 456,
    qty: 30
  },
  {
    id: 123,
    qty: 20
  },
  {
    id: 456,
    qty: 30
  },
  {
    id: 456,
    qty: 30
  }
]

var priceMap = new Map();
var dataArray = [123, 456];
var qty = 0;
for (var i = 0; i < dataArray.length; i++) {
  for (var j = 0; j < data.length; j++) {
    if (dataArray[i] == data[j].id) {
        var qty = qty + data[j].qty;
            priceMap.set(dataArray[i], qty);
    }
  }
   qty = 0;   <- here
}

console.log(priceMap.get(123), priceMap.get(456))
//expected outcome -- priceMap.get(123) -> 40 and priceMap.get(456) -> 90

edited Aug 9, 2020 at 2:28

answered Aug 9, 2020 at 2:23

Stark Jeon

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2 Comments

soum Over a year ago

Yep..that did it. Thanks :-)

Stark Jeon Over a year ago

Good luck to you 👍🏻

charlietfl · Accepted Answer · 2020-08-09 02:38:57Z

1

You really only need to loop through the array once to create the Map. Here I've done it with a fairly straightforward reduce() but other loop methods could be used also

const data=[{id:123,qty:20},{id:456,qty:30},{id:123,qty:20},{id:456,qty:30},{id:456,qty:30}];

const pMap = data.reduce((m, {id, qty}) => m.set(id, (m.get(id) || 0) + qty), new Map)

console.log(pMap.get(123), pMap.get(456) )

edited Aug 9, 2020 at 2:38

answered Aug 9, 2020 at 2:27

charlietfl

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