CODEWITHSUNDEEP
javascriptarrays
Piyush
Piyush

Reputation: 85

how to count keys present in array of object in javascript?

I have an below array. I wanted to know how many time selectedOption key is present in array of Object. In, some object we don't have key selectedOption. So, the count of key selectedOption should return 4. How we can count these key in javascript ?

let data = [{
  id: 123,
  selectedOption: "ABC",
  value: 345
}, {
  id: 234,
  selectedOption: "BCD",
  value: 345
}, {
  id: 356,
  selectedOption: "BGY",
  value: 678
}, {
  id: 456,
  selectedOption: "BCD",
  value: 890
}, {
  id: 870: value: 980
}, {
  id: 385,
  value: 654
}]

Upvotes: 1

Views: 98

Answers (3)

hendrixchord
hendrixchord

Reputation: 5434

data.filter(d => d.hasOwnProperty('selectedOption')).length

This is a more full proof solution compared to data.filter(datum => datum.selectedOption).length because if selectedOption was a boolean flag with false value it wouldn't be counted.

hasOwnProperty will check if the property exists on the object irrespective of the value.

For example in this case

let data = [{
  id: 123,
  selectedOption: false,
  value: 345
}, {
  id: 234,
  selectedOption: false,
  value: 345
}, {
  id: 356,
  selectedOption: true,
  value: 678
}, {
  id: 456,
  selectedOption: false,
  value: 890
}, {
  id: 870,
  value: 980
}, {
  id: 385,
  value: 654
}];

  1. data.filter(d => d.hasOwnProperty('selectedOption')).length Output: 4

  2. data.filter(datum => datum.selectedOption).length Output: 1

Upvotes: 1

brk
brk

Reputation: 50291

There are multiple ways it can be done. In the below function ,reduce is used. Inside reduce callback it is checking if the object has selectedOption key then increment 1 

let data = [{
  id: 123,
  selectedOption: "ABC",
  value: 345
}, {
  id: 234,
  selectedOption: "BCD",
  value: 345
}, {
  id: 356,
  selectedOption: "BGY",
  value: 678
}, {
  id: 456,
  selectedOption: "BCD",
  value: 890
}, {
  id: 870,
  value: 980
}, {
  id: 385,
  value: 654
}];

let countSelectedOption = data.reduce((acc, curr) => {
  acc += curr.selectedOption ? 1 : 0;
  return acc;
}, 0);
console.log(countSelectedOption)

Upvotes: 0

Nicky McCurdy
Nicky McCurdy

Reputation: 19524

data.filter(datum => datum.selectedOption).length

Upvotes: 6

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