How to check two arrays of object has the same property value or not?

Question

i have two arrays and want to check if all IDs is the same or not

let a = [
          {id:0, name:"test0"},
          {id:1, name:"test1"}
         ];

let b = [
          {id:0, name:"test0"},
          {id:1, name:"test1"}
         ];

the above arrays we see it's equal

and the way I tired like this

JSON.stringify(a) === JSON.stringify(b) => True

I read the JSON.stringify it's affected the Performance if we have big arrays

so is there another way to get the same result?

Majed Badawi · Accepted Answer · 2021-05-31T22:43:52.367

2

const areEqual = (a = [], b = []) => {
  // compare length of arrays
  if(a.length !== b.length) {
    return false;
  }
  // get sorted lists of ids
  const arr1 = a.map(({id}) => id).sort(), arr2 = b.map(({id}) => id).sort();
  // iterate over the arrays and compare, if at an index, items mismatch, return false
  for(let i = 0; i < arr1.length; i++) {
    if(arr1[i] !== arr2[i]) {
      return false;
    }
  }
  // if it passes all the items, return true
  return true;
}

console.log( 
  areEqual(
    [{id:0, name:"test0"}, {id:1, name:"test1"}], 
    [{id:0, name:"test0"}, {id:1, name:"test1"}]
  )
);

Another solution using Set:

const areEqual = (a = [], b = []) => {
  // compare length of arrays
  if(a.length !== b.length) {
    return false;
  }
  // get ids set in b
  const idsSetInB = new Set(b.map(({id}) => id));
  // iterate over a, and check if the id of an item is not in b
  for(let {id} of a) {
    if(!idsSetInB.has(id)) {
      return false;
    }
  }
  // if it passes all the items, return true
  return true;
}

console.log( 
  areEqual(
    [{id:0, name:"test0"}, {id:1, name:"test1"}], 
    [{id:1, name:"test1"}, {id:0, name:"test0"}]
  )
);

edited May 31 '21 at 22:43

answered May 31 '21 at 21:57

Majed Badawi

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2

Nice code. I'll point out that any solution will be O(N) for performance. Longer arrays will require more work to process regardless. – duffymo May 31 '21 at 22:22
Thanks, What the issues with the first answer before the Edit? `_getIds(a).sort().join(',')` – Oliver D May 31 '21 at 22:29
@OliverD it works, but I edited the solution in case you want to check for types as well. – Majed Badawi May 31 '21 at 22:33
Question, are ids unique in each array? – Majed Badawi May 31 '21 at 22:34
@MajedBadawi yes it's unique! – Oliver D May 31 '21 at 22:38
I added another approach which should handle big arrays better. @duffymo thanks for the comment, feel free to suggest changes/other approaches. – Majed Badawi May 31 '21 at 22:45
@MajedBadawi Thanks, i learn new things today^^ – Oliver D Jun 01 '21 at 18:12
Hey @MajedBadawi can you please check the Edit section, thanks? – Oliver D Jun 03 '21 at 17:44
@MajedBadawi can you please check this [https://stackoverflow.com/questions/67849438/cant-synchronise-the-updated-array-in-zustand][Q] I Separated it "if u have checked the Edit Section" – Oliver D Jun 05 '21 at 12:43

How to check two arrays of object has the same property value or not?

1 Answers1