CODEWITHSUNDEEP
javascriptlodash
Carol.Kar
Carol.Kar

Reputation: 5345

Sum up array with objects

I am having the following array with objects and I would like to sum up all occurrences of watt:

let allProducts = [{
    "unique_id": "102",
    "currency": "$",
    "price": "529.99",
    "watt": 150
  },
  {
    "unique_id": "11",
    "currency": "$",
    "price": "323",
    "watt": 150
  },
  {
    "unique_id": "13",
    "currency": "$",
    "price": "23",
    "watt": 77
  }
]

let getWatt =
  _(allProducts)
  .map((objs, key) => ({
    'watt': _.sumBy(objs, 'watt')
  }))
  .value()

console.log(getWatt)
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

As you can see I get back an array of 0 values. However, I would like to get back the result value of 377. Any suggestions what I am doing wrong?

I appreciate your replies!

Upvotes: 4

Views: 13249

Answers (4)

Nina Scholz
Nina Scholz

Reputation: 386520

Just take a single _.sumBy with the array of objects and the wanted key watt for summing.

Your attempt uses an object, instead of an array for _.sumBy. The object is not an array and the return value is zero.

var allProducts = [{ unique_id: "102", currency: "$", price: "529.99", watt: 150 }, { unique_id: "11", currency: "$", price: "323", watt: 150 }, { unique_id: "13", currency: "$", price: "23", watt: 77 }],
    getWatt = _.sumBy(allProducts, 'watt');

console.log(getWatt)
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

Upvotes: 1

Muhammad Usman
Muhammad Usman

Reputation: 10148

I've read the answers, but I'd like to add an explanation to your problem. The reason you're getting an array is because of using .map. As map returns you the array not a single element. Moreover, you are expecting to get the returned array as modified and map doesn't do that.

What you're trying to achieve is can be done using .reduce. I mean that's why .reduce is there 

let allProducts = [{
    "unique_id": "102",
    "currency": "$",
    "price": "529.99",
    "watt": 150
  },
  {
    "unique_id": "11",
    "currency": "$",
    "price": "323",
    "watt": 150
  },
  {
    "unique_id": "13",
    "currency": "$",
    "price": "23",
    "watt": 77
  }
];
var getWatt = allProducts.reduce((acc,curr)=> acc + curr.watt,0);
console.log(getWatt);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

Upvotes: 4

amrender singh
amrender singh

Reputation: 8239

Try the following:

let allProducts = [{
    "unique_id": "102",
    "currency": "$",
    "price": "529.99",
    "watt": 150
  },
  {
    "unique_id": "11",
    "currency": "$",
    "price": "323",
    "watt": 150
  },
  {
    "unique_id": "13",
    "currency": "$",
    "price": "23",
    "watt": 77
  }
];

var sum = allProducts.reduce((sum,a)=>{
  return sum + a.watt;
},0);
console.log(sum);

Upvotes: 1

baao
baao

Reputation: 73211

It's easy using plain js

const sum = allProducts.reduce((a, {watt}) => a + watt, 0);
console.log(sum);
<script>
let allProducts = [{
    "unique_id": "102",
    "currency": "$",
    "price": "529.99",
    "watt": 150
  },
  {
    "unique_id": "11",
    "currency": "$",
    "price": "323",
    "watt": 150
  },
  {
    "unique_id": "13",
    "currency": "$",
    "price": "23",
    "watt": 77
  }
]


</script>

Upvotes: 15

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