How to check if all objects in an array contains same keys and values?

Question

How to check if all objects in an array contains same keys and values

const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2}, {a:1, b: 2 }] // true

const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2}, {a:2, b: 1 }] //false

const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2, c: 3}, {a:2, b: 1 }] //false

This is my trial that looks so ugly and bad and not working, i would be thankful if someone put an efficient code for that problem!

function test(arr){

   const firstItem = arr[0];
   const firstItemKeys = Object.keys(firstItem);

   for(let i = 0; i < firstItemKeys.length; i++) {
      for(let j = 0; j < arr.length; j++) {
         for(let x in arr[j]) {
             if(arr[j][x] !== firstItem[firstItemKeys[i]]) return false
         }
       }
   }

   return true
}

See stackoverflow.com/questions/201183/… for ways to check if objects are equal. Then just use one of those techniques in the loop. — Barmar
– Barmar, Commented Jun 18, 2020 at 23:53
Some important restrictions for this question: Are outside libraries acceptable? Are the objects always a single level deep, or might they be nested? Can you confirm if values will always be scalar values? These will be important considerations for answering this to your requirements. — Alexander Nied
– Alexander Nied, Commented Jun 18, 2020 at 23:55
@AlexanderNied no i don't want to use libraries, and no no nested objects and values not always scalar — Code Eagle
– Code Eagle, Commented Jun 18, 2020 at 23:59

Rahul Bhobe · Accepted Answer · 2020-06-19 13:14:51Z

3

Here is the code:

const arrOfObjects = [
  { a: 1, b: 2 },
  { a: 1, b: 2 },
  { b: 2, a: 1 },
]
function areEquals(a, b) {
  var keys1 = Object.keys(a)
  var keys2 = Object.keys(b)
  if(keys1.length !== keys2.length) {
    return false ;
  }
  for(key in a) {
    if(a[key] !== b[key])  return false;
  }
  return true ;
}
function checkArray(arr) {
  for (var i = 1; i < arr.length; i++) {
    if (!areEquals(arr[0], arr[i])) return false
  }
  return true
}
console.log(checkArray(arrOfObjects))

edited Jun 19, 2020 at 13:14

Rahul Bhobe

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answered Jun 19, 2020 at 0:04

Ehsan Nazeri

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3 Comments

Orilious Over a year ago

If you switch the position of a and b in one object like { b: 2, a: 1 } it'll return false.

Code Eagle Over a year ago

yes i was writing that comment the moment i saw yours @Armamedia

Always Helping Over a year ago

@EhsanNazeri this will not work as OP as wanted if you have [{a: 1, b: 2}, {a: 1, b: 2, c: 3}, {a:2, b: 1 }] like this. just FYI

libik · Accepted Answer · 2020-06-19 00:00:22Z

2

If you can use lodash, then there is method _.isEqual

const _ = require('lodash')
const arrOfObjects = [{a: 1, b: 2}, {a: 1, b: 2}, {a:1, b: 2 }]
let isEqual = true
arrOfObjects.forEach(obj => {
  if (!_.isEqual(arrOfObjects[0], obj)) {
    isEqual = false
  } 
})

return isEqual

PS: This could be written in one line with reduce, but it will not be readable for anyone new to programming or javascript.

answered Jun 19, 2020 at 0:00

libik

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2 Comments

Alexander Nied Over a year ago

Unfortunately the user indicated in the comments that outside libraries are not acceptable.

Always Helping Over a year ago

The OP said he does want to use libraries. So this will not help.

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