adding items length of an object

Question

I have an object with some array items, now I have to calculate the length of all items. I got an idea to calculate these items, I declared count = 0 variable, then calculated these items length & added with count variable.

var obj = {
  item_1: ['item1', 'item2', 'item3', 'item4'],
  item_2: ['item1', 'item2', 'item3', 'item4', 'item5'],
  item_3: ['item1', 'item2', 'item3']
}

var count = 0;

Object.entries(obj).map(item => {
  count += item[1].length
})

console.log(count)

My question is: how can I get this result without declaring calculate variable? example: console.log(Object.entries(Obj)....?)

What is the `calculate` variable? Do you mean `count`? – Barmar Aug 11 '18 at 14:10 — Barmar, Aug 11 '18 at 14:10

Jonas Wilms · Accepted Answer · 2018-08-11T13:39:38.950

8

You are looking for reduce:

  Object.values(obj).reduce((sum, subarr) => sum + subarr.length, 0)

This is one of the rare good usecases for it, there are a lot of other cases were reduce actually complicates the code, so going with global variables is sometimes the better approach.

edited Aug 11 '18 at 13:39

answered Aug 11 '18 at 13:34

Jonas Wilms

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`subarr.length` will return the key length, It should be `subarr[1].length` – Delowar Hosain Aug 11 '18 at 13:43
1

@DelowarHosain I think you are confusing `Object.entries()` with `Object.values()` – charlietfl Aug 11 '18 at 13:44
1

Wow, a kindred spirit who thinks most `reduce` uses are confusing! – Barmar Aug 11 '18 at 14:11

score 0 · Answer 2 · answered Aug 11 '18 at 13:50

0

you can do

[].concat.apply([], Object.values(obj)).length

or using ES6

[].concat(...Object.values(obj)).length

i am just adding one more step to Merge/flatten an array of arrays in JavaScript?

answered Aug 11 '18 at 13:50

ashish singh

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adding items length of an object

2 Answers2