How To Group Object Using reduce Function javascript

Question

I have been stuck on this for 8 days now.

Let's say here is my response object array:

var items = [
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
{
    name: 'hp-44',
    price: 100,
    id: 10,
},
{
    name: 'acer-33',
    price: 250,
    id: 33,
},
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
{
    name: 'acer-33',
    price: 250,
    id: 33,
},
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
]

So far i have managed to make a function using reduce to accumulate the price. Here is the code that does this:

var obj = items.reduce( function (allItems, currentItem) {
var item_name = currentItem.name;
var item_price = currentItem.price;


var total_prices = allItems[item_price] = (allItems[item_price] || 0) +   
item_price;


var result = {};

result[item_name] = {
    item_price:  total_prices,
}


return Object.assign(allItems, result);
}, {} )

Although this works, it does not return the results i want, instead it returns this:

{
'100': 100,
'200': 600,
'250': 500,
'dell-66': { item_price: 600 },
'hp-44': { item_price: 100 },
'acer-33': { item_price: 500 } 
 }

Here is what i intended and need it to be (without the extra key/values at the top):

{
'dell-66': { item_price: 600 },
'hp-44': { item_price: 100 },
'acer-33': { item_price: 500 } 
 }

How Can i achieve this please?

Olian04 · Accepted Answer · 2018-07-08 14:38:33Z

7

You could do it like this.

const items = [{
    name: 'dell-66',
    price: 200,
    id: 12,
  }, {
    name: 'hp-44',
    price: 100,
    id: 10,
  }, {
    name: 'acer-33',
    price: 250,
    id: 33,
  }, {
    name: 'dell-66',
    price: 200,
    id: 12,
  }, {
    name: 'acer-33',
    price: 250,
    id: 33,
  }, {
    name: 'dell-66',
    price: 200,
    id: 12,
  },
].reduce((res, obj) => {
  res[obj.name] = { 
    item_price: (obj.name in res ? res[obj.name].item_price : 0) + obj.price 
  }
  return res;
}, {})

console.log(items);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Jul 8, 2018 at 14:38

answered Jul 8, 2018 at 14:01

Olian04

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2 Comments

Victor Ijishakin Over a year ago

Holy Moly! This Works! Thank you! But could you maybe explain what had been the problem with my code?

Olian04 Over a year ago

@ViveeOmomi Well, to start off with, allItems[item_price] is looking for a key of item_price in allItems. Aka: { '100': value} not (As i think you were going for) a key where its value is item_price, Aka: { key: 100 }

mickl · Accepted Answer · 2018-07-08 14:04:32Z

3

You can use following code:

var items = [
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
{
    name: 'hp-44',
    price: 100,
    id: 10,
},
{
    name: 'acer-33',
    price: 250,
    id: 33,
},
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
{
    name: 'acer-33',
    price: 250,
    id: 33,
},
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
]

let result = items.reduce((result, current) => {
	if(!result[current.name]){
		result[current.name] = { item_price: 0 };
	}
	result[current.name].item_price += current.price;
	return result;
}, {})

console.log(result);

answered Jul 8, 2018 at 14:04

mickl

50.1k9 gold badges71 silver badges99 bronze badges

Comments

Lead Developer · Accepted Answer · 2018-07-08 14:08:16Z

3

You can use the map function for this. Please try following code.

var items = [
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
{
    name: 'hp-44',
    price: 100,
    id: 10,
},
{
    name: 'acer-33',
    price: 250,
    id: 33,
},
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
{
    name: 'acer-33',
    price: 250,
    id: 33,
},
{
    name: 'dell-66',
    price: 200,
    id: 12,
},
]

var rlt = {};

items.map(item => {
  let price = item.price
  let name = item.name
  if (rlt[name]) {
    rlt[name] = rlt[name] + price
  } else {
    rlt[name] = price;
  }
});
console.log(rlt);

answered Jul 8, 2018 at 14:08

Lead Developer

1,16710 silver badges26 bronze badges

6 Comments

Olian04 Over a year ago

Why not use Array#reduce?

Lead Developer Over a year ago

we can use reduce too for this. but I was going to show several solution.

Olian04 Over a year ago

I'm aware :) I'm just asking why you opted not to. I'm curious.

Victor Ijishakin Over a year ago

Thank You, I am So glad you answered, i was wondering if Array#map could ever do this, now i know better, glad to have diverse solutions.

Lead Developer Over a year ago

@ViveeOmomi I'm glad this could help you.

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